diff --git a/aof.go b/aof.go
index 93ec7c5..7b1b338 100644
--- a/aof.go
+++ b/aof.go
@@ -19,11 +19,11 @@ import (
 	"time"
 )
 
-var pExpireAtCmd = []byte("PEXPIREAT")
+var pExpireAtBytes = []byte("PEXPIREAT")
 
 func makeExpireCmd(key string, expireAt time.Time) *reply.MultiBulkReply {
 	args := make([][]byte, 3)
-	args[0] = pExpireAtCmd
+	args[0] = pExpireAtBytes
 	args[1] = []byte(key)
 	args[2] = []byte(strconv.FormatInt(expireAt.UnixNano()/1e6, 10))
 	return reply.MakeMultiBulkReply(args)
@@ -101,9 +101,10 @@ func (db *DB) loadAof(maxBytes int) {
 			continue
 		}
 		cmd := strings.ToLower(string(r.Args[0]))
-		cmdFunc, ok := router[cmd]
+		command, ok := cmdTable[cmd]
 		if ok {
-			cmdFunc(db, r.Args[1:])
+			handler := command.executor
+			handler(db, r.Args[1:])
 		}
 	}
 }
diff --git a/aof_test.go b/aof_test.go
index ee90ea1..84eefb7 100644
--- a/aof_test.go
+++ b/aof_test.go
@@ -34,31 +34,31 @@ func TestAof(t *testing.T) {
 	for i := 0; i < size; i++ {
 		key := strconv.Itoa(cursor)
 		cursor++
-		Set(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8), "EX", "10000"))
+		execSet(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8), "EX", "10000"))
 		keys = append(keys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := strconv.Itoa(cursor)
 		cursor++
-		RPush(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
+		execRPush(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := strconv.Itoa(cursor)
 		cursor++
-		HSet(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8), utils2.RandString(8)))
+		execHSet(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8), utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := strconv.Itoa(cursor)
 		cursor++
-		SAdd(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
+		execSAdd(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := strconv.Itoa(cursor)
 		cursor++
-		ZAdd(aofWriteDB, utils2.ToBytesList(key, "10", utils2.RandString(8)))
+		execZAdd(aofWriteDB, utils2.ToBytesList(key, "10", utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	aofWriteDB.Close()    // wait for aof finished
@@ -105,44 +105,44 @@ func TestRewriteAOF(t *testing.T) {
 	for i := 0; i < size; i++ {
 		key := "str" + strconv.Itoa(cursor)
 		cursor++
-		Set(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
-		Set(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
+		execSet(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
+		execSet(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	// test ttl
 	for i := 0; i < size; i++ {
 		key := "str" + strconv.Itoa(cursor)
 		cursor++
-		Set(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8), "EX", "1000"))
+		execSet(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8), "EX", "1000"))
 		ttlKeys = append(ttlKeys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := "list" + strconv.Itoa(cursor)
 		cursor++
-		RPush(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
-		RPush(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
+		execRPush(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
+		execRPush(aofWriteDB, utils2.ToBytesList(key, utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := "hash" + strconv.Itoa(cursor)
 		cursor++
 		field := utils2.RandString(8)
-		HSet(aofWriteDB, utils2.ToBytesList(key, field, utils2.RandString(8)))
-		HSet(aofWriteDB, utils2.ToBytesList(key, field, utils2.RandString(8)))
+		execHSet(aofWriteDB, utils2.ToBytesList(key, field, utils2.RandString(8)))
+		execHSet(aofWriteDB, utils2.ToBytesList(key, field, utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := "set" + strconv.Itoa(cursor)
 		cursor++
 		member := utils2.RandString(8)
-		SAdd(aofWriteDB, utils2.ToBytesList(key, member))
-		SAdd(aofWriteDB, utils2.ToBytesList(key, member))
+		execSAdd(aofWriteDB, utils2.ToBytesList(key, member))
+		execSAdd(aofWriteDB, utils2.ToBytesList(key, member))
 		keys = append(keys, key)
 	}
 	for i := 0; i < size; i++ {
 		key := "zset" + strconv.Itoa(cursor)
 		cursor++
-		ZAdd(aofWriteDB, utils2.ToBytesList(key, "10", utils2.RandString(8)))
+		execZAdd(aofWriteDB, utils2.ToBytesList(key, "10", utils2.RandString(8)))
 		keys = append(keys, key)
 	}
 	time.Sleep(time.Second) // wait for async goroutine finish its job
@@ -167,7 +167,7 @@ func TestRewriteAOF(t *testing.T) {
 		}
 	}
 	for _, key := range ttlKeys {
-		ret := TTL(aofReadDB, utils2.ToBytesList(key))
+		ret := execTTL(aofReadDB, utils2.ToBytesList(key))
 		intResult, ok := ret.(*reply.IntReply)
 		if !ok {
 			t.Errorf("expected int reply, actually %s", ret.ToBytes())
diff --git a/cluster/rename_test.go b/cluster/rename_test.go
index 03f7678..5c1fcc8 100644
--- a/cluster/rename_test.go
+++ b/cluster/rename_test.go
@@ -2,7 +2,6 @@ package cluster
 
 import (
 	"fmt"
-	"github.com/hdt3213/godis"
 	"github.com/hdt3213/godis/lib/utils"
 	"github.com/hdt3213/godis/redis/reply"
 	"github.com/hdt3213/godis/redis/reply/asserts"
@@ -11,22 +10,22 @@ import (
 
 func TestRename(t *testing.T) {
 	testDB := testCluster.db
-	godis.FlushAll(testDB, [][]byte{})
+	testDB.Exec(nil, utils.ToBytesList("FlushALL"))
 	key := utils.RandString(10)
 	value := utils.RandString(10)
 	newKey := key + utils.RandString(2)
-	godis.Set(testDB, utils.ToBytesList(key, value, "ex", "1000"))
+	testDB.Exec(nil, utils.ToBytesList("SET", key, value, "ex", "1000"))
 	result := Rename(testCluster, nil, utils.ToBytesList("RENAME", key, newKey))
 	if _, ok := result.(*reply.OkReply); !ok {
 		t.Error("expect ok")
 		return
 	}
-	result = godis.Exists(testDB, utils.ToBytesList(key))
+	result = testDB.Exec(nil, utils.ToBytesList("EXISTS", key))
 	asserts.AssertIntReply(t, result, 0)
-	result = godis.Exists(testDB, utils.ToBytesList(newKey))
+	result = testDB.Exec(nil, utils.ToBytesList("EXISTS", newKey))
 	asserts.AssertIntReply(t, result, 1)
 	// check ttl
-	result = godis.TTL(testDB, utils.ToBytesList(newKey))
+	result = testDB.Exec(nil, utils.ToBytesList("TTL", newKey))
 	intResult, ok := result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
@@ -40,18 +39,19 @@ func TestRename(t *testing.T) {
 
 func TestRenameNx(t *testing.T) {
 	testDB := testCluster.db
-	godis.FlushAll(testDB, [][]byte{})
+	testDB.Exec(nil, utils.ToBytesList("FlushALL"))
 	key := utils.RandString(10)
 	value := utils.RandString(10)
 	newKey := key + utils.RandString(2)
-	godis.Set(testCluster.db, utils.ToBytesList(key, value, "ex", "1000"))
+	testCluster.db.Exec(nil, utils.ToBytesList("SET", key, value, "ex", "1000"))
 	result := RenameNx(testCluster, nil, utils.ToBytesList("RENAMENX", key, newKey))
 	asserts.AssertIntReply(t, result, 1)
-	result = godis.Exists(testDB, utils.ToBytesList(key))
+	result = testDB.Exec(nil, utils.ToBytesList("EXISTS", key))
 	asserts.AssertIntReply(t, result, 0)
-	result = godis.Exists(testDB, utils.ToBytesList(newKey))
+	result = testDB.Exec(nil, utils.ToBytesList("EXISTS", newKey))
+
 	asserts.AssertIntReply(t, result, 1)
-	result = godis.TTL(testDB, utils.ToBytesList(newKey))
+	result = testDB.Exec(nil, utils.ToBytesList("TTL", newKey))
 	intResult, ok := result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
diff --git a/db.go b/db.go
index 32d48ff..1fb1183 100644
--- a/db.go
+++ b/db.go
@@ -2,7 +2,6 @@
 package godis
 
 import (
-	"fmt"
 	"github.com/hdt3213/godis/config"
 	"github.com/hdt3213/godis/datastruct/dict"
 	"github.com/hdt3213/godis/datastruct/lock"
@@ -12,17 +11,10 @@ import (
 	"github.com/hdt3213/godis/pubsub"
 	"github.com/hdt3213/godis/redis/reply"
 	"os"
-	"runtime/debug"
-	"strings"
 	"sync"
 	"time"
 )
 
-// DataEntity stores data bound to a key, including a string, list, hash, set and so on
-type DataEntity struct {
-	Data interface{}
-}
-
 const (
 	dataDictSize = 1 << 16
 	ttlDictSize  = 1 << 10
@@ -30,9 +22,6 @@ const (
 	aofQueueSize = 1 << 16
 )
 
-// args don't include cmd line
-type cmdFunc func(db *DB, args [][]byte) redis.Reply
-
 // DB stores data and execute user's commands
 type DB struct {
 	// key -> DataEntity
@@ -43,7 +32,7 @@ type DB struct {
 	// dict.Dict will ensure concurrent-safety of its method
 	// use this mutex for complicated command only, eg. rpush, incr ...
 	locker *lock.Locks
-	// stop all data access for FlushDB
+	// stop all data access for execFlushDB
 	stopWorld sync.WaitGroup
 	// handle publish/subscribe
 	hub *pubsub.Hub
@@ -60,7 +49,18 @@ type DB struct {
 	pausingAof sync.RWMutex
 }
 
-var router = makeRouter()
+// PreFunc analyses command line when queued command to `multi`
+// returns related keys and undo commands
+type PreFunc func(args [][]byte) ([]string, [][][]byte)
+
+// ExecFunc is interface for command executor
+// args don't include cmd line
+type ExecFunc func(db *DB, args [][]byte) redis.Reply
+
+// DataEntity stores data bound to a key, including a string, list, hash, set and so on
+type DataEntity struct {
+	Data interface{}
+}
 
 // MakeDB create DB instance and start it
 func MakeDB() *DB {
@@ -102,49 +102,12 @@ func (db *DB) Close() {
 	}
 }
 
-// Exec executes command
-// parameter `cmdArgs` contains command and its arguments, for example: "set key value"
-func (db *DB) Exec(c redis.Connection, cmdArgs [][]byte) (result redis.Reply) {
-	defer func() {
-		if err := recover(); err != nil {
-			logger.Warn(fmt.Sprintf("error occurs: %v\n%s", err, string(debug.Stack())))
-			result = &reply.UnknownErrReply{}
-		}
-	}()
-
-	cmd := strings.ToLower(string(cmdArgs[0]))
-	if cmd == "auth" {
-		return Auth(db, c, cmdArgs[1:])
+func validateArity(arity int, cmdArgs [][]byte) bool {
+	argNum := len(cmdArgs)
+	if arity >= 0 {
+		return argNum == arity
 	}
-	if !isAuthenticated(c) {
-		return reply.MakeErrReply("NOAUTH Authentication required")
-	}
-	// special commands
-	if cmd == "subscribe" {
-		if len(cmdArgs) < 2 {
-			return &reply.ArgNumErrReply{Cmd: "subscribe"}
-		}
-		return pubsub.Subscribe(db.hub, c, cmdArgs[1:])
-	} else if cmd == "publish" {
-		return pubsub.Publish(db.hub, cmdArgs[1:])
-	} else if cmd == "unsubscribe" {
-		return pubsub.UnSubscribe(db.hub, c, cmdArgs[1:])
-	} else if cmd == "bgrewriteaof" {
-		// aof.go imports router.go, router.go cannot import BGRewriteAOF from aof.go
-		return BGRewriteAOF(db, cmdArgs[1:])
-	}
-
-	// normal commands
-	fun, ok := router[cmd]
-	if !ok {
-		return reply.MakeErrReply("ERR unknown command '" + cmd + "'")
-	}
-	if len(cmdArgs) > 1 {
-		result = fun(db, cmdArgs[1:])
-	} else {
-		result = fun(db, [][]byte{})
-	}
-	return
+	return argNum >= -arity
 }
 
 /* ---- Data Access ----- */
@@ -263,7 +226,7 @@ func genExpireTask(key string) string {
 	return "expire:" + key
 }
 
-// Expire sets TTL of key
+// Expire sets ttlCmd of key
 func (db *DB) Expire(key string, expireTime time.Time) {
 	db.stopWorld.Wait()
 	db.ttlMap.Put(key, expireTime)
@@ -274,7 +237,7 @@ func (db *DB) Expire(key string, expireTime time.Time) {
 	})
 }
 
-// Persist cancel TTL of key
+// Persist cancel ttlCmd of key
 func (db *DB) Persist(key string) {
 	db.stopWorld.Wait()
 	db.ttlMap.Remove(key)
diff --git a/exec.go b/exec.go
new file mode 100644
index 0000000..6fa0a10
--- /dev/null
+++ b/exec.go
@@ -0,0 +1,63 @@
+package godis
+
+import (
+	"fmt"
+	"github.com/hdt3213/godis/interface/redis"
+	"github.com/hdt3213/godis/lib/logger"
+	"github.com/hdt3213/godis/pubsub"
+	"github.com/hdt3213/godis/redis/reply"
+	"runtime/debug"
+	"strings"
+)
+
+// Exec executes command
+// parameter `cmdArgs` contains command and its arguments, for example: "set key value"
+func (db *DB) Exec(c redis.Connection, cmdArgs [][]byte) (result redis.Reply) {
+	defer func() {
+		if err := recover(); err != nil {
+			logger.Warn(fmt.Sprintf("error occurs: %v\n%s", err, string(debug.Stack())))
+			result = &reply.UnknownErrReply{}
+		}
+	}()
+
+	cmdName := strings.ToLower(string(cmdArgs[0]))
+	// authenticate
+	if cmdName == "auth" {
+		return Auth(db, c, cmdArgs[1:])
+	}
+	if !isAuthenticated(c) {
+		return reply.MakeErrReply("NOAUTH Authentication required")
+	}
+
+	// special commands
+	if cmdName == "subscribe" {
+		if len(cmdArgs) < 2 {
+			return reply.MakeArgNumErrReply("subscribe")
+		}
+		return pubsub.Subscribe(db.hub, c, cmdArgs[1:])
+	} else if cmdName == "publish" {
+		return pubsub.Publish(db.hub, cmdArgs[1:])
+	} else if cmdName == "unsubscribe" {
+		return pubsub.UnSubscribe(db.hub, c, cmdArgs[1:])
+	} else if cmdName == "bgrewriteaof" {
+		// aof.go imports router.go, router.go cannot import BGRewriteAOF from aof.go
+		return BGRewriteAOF(db, cmdArgs[1:])
+	}
+
+	// normal commands
+	cmd, ok := cmdTable[cmdName]
+	if !ok {
+		return reply.MakeErrReply("ERR unknown command '" + cmdName + "'")
+	}
+	if !validateArity(cmd.arity, cmdArgs) {
+		return reply.MakeArgNumErrReply(cmdName)
+	}
+
+	fun := cmd.executor
+	if len(cmdArgs) > 1 {
+		result = fun(db, cmdArgs[1:])
+	} else {
+		result = fun(db, [][]byte{})
+	}
+	return
+}
diff --git a/geo.go b/geo.go
index dd08d14..e062eb8 100644
--- a/geo.go
+++ b/geo.go
@@ -10,8 +10,8 @@ import (
 	"strings"
 )
 
-// GeoAdd add a location into SortedSet
-func GeoAdd(db *DB, args [][]byte) redis.Reply {
+// execGeoAdd add a location into SortedSet
+func execGeoAdd(db *DB, args [][]byte) redis.Reply {
 	if len(args) < 4 || len(args)%3 != 1 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'geoadd' command")
 	}
@@ -61,8 +61,8 @@ func GeoAdd(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(i))
 }
 
-// GeoPos returns location of a member
-func GeoPos(db *DB, args [][]byte) redis.Reply {
+// execGeoPos returns location of a member
+func execGeoPos(db *DB, args [][]byte) redis.Reply {
 	// parse args
 	if len(args) < 1 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'geopos' command")
@@ -94,8 +94,8 @@ func GeoPos(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiRawReply(positions)
 }
 
-// GeoDist returns the distance between two locations
-func GeoDist(db *DB, args [][]byte) redis.Reply {
+// execGeoDist returns the distance between two locations
+func execGeoDist(db *DB, args [][]byte) redis.Reply {
 	// parse args
 	if len(args) != 3 && len(args) != 4 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'geodist' command")
@@ -135,8 +135,8 @@ func GeoDist(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeErrReply("ERR unsupported unit provided. please use m, km")
 }
 
-// GeoHash return geo-hash-code of given position
-func GeoHash(db *DB, args [][]byte) redis.Reply {
+// execGeoHash return geo-hash-code of given position
+func execGeoHash(db *DB, args [][]byte) redis.Reply {
 	// parse args
 	if len(args) < 1 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'geohash' command")
@@ -165,8 +165,8 @@ func GeoHash(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(strs)
 }
 
-// GeoRadius returns members within max distance of given point
-func GeoRadius(db *DB, args [][]byte) redis.Reply {
+// execGeoRadius returns members within max distance of given point
+func execGeoRadius(db *DB, args [][]byte) redis.Reply {
 	// parse args
 	if len(args) < 5 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'georadius' command")
@@ -203,8 +203,8 @@ func GeoRadius(db *DB, args [][]byte) redis.Reply {
 	return geoRadius0(sortedSet, lat, lng, radius)
 }
 
-// GeoRadiusByMember returns members within max distance of given member's location
-func GeoRadiusByMember(db *DB, args [][]byte) redis.Reply {
+// execGeoRadiusByMember returns members within max distance of given member's location
+func execGeoRadiusByMember(db *DB, args [][]byte) redis.Reply {
 	// parse args
 	if len(args) < 3 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'georadiusbymember' command")
@@ -255,3 +255,12 @@ func geoRadius0(sortedSet *sortedset.SortedSet, lat float64, lng float64, radius
 	}
 	return reply.MakeMultiBulkReply(members)
 }
+
+func init() {
+	RegisterCommand("GeoAdd", execGeoAdd, nil, -5)
+	RegisterCommand("GeoPos", execGeoPos, nil, -2)
+	RegisterCommand("GeoDist", execGeoDist, nil, -4)
+	RegisterCommand("GeoHash", execGeoHash, nil, -2)
+	RegisterCommand("GeoRadius", execGeoRadius, nil, -6)
+	RegisterCommand("GeoRadiusByMember", execGeoRadiusByMember, nil, -5)
+}
diff --git a/geo_test.go b/geo_test.go
index c5ec96c..1e73abf 100644
--- a/geo_test.go
+++ b/geo_test.go
@@ -10,52 +10,52 @@ import (
 )
 
 func TestGeoHash(t *testing.T) {
-	FlushDB(testDB, utils.ToBytesList())
+	execFlushDB(testDB, utils.ToBytesList())
 	key := utils.RandString(10)
 	pos := utils.RandString(10)
-	result := GeoAdd(testDB, utils.ToBytesList(key, "13.361389", "38.115556", pos))
+	result := execGeoAdd(testDB, utils.ToBytesList(key, "13.361389", "38.115556", pos))
 	asserts.AssertIntReply(t, result, 1)
-	result = GeoHash(testDB, utils.ToBytesList(key, pos))
+	result = execGeoHash(testDB, utils.ToBytesList(key, pos))
 	asserts.AssertMultiBulkReply(t, result, []string{"sqc8b49rnys00"})
 }
 
 func TestGeoRadius(t *testing.T) {
-	FlushDB(testDB, utils.ToBytesList())
+	execFlushDB(testDB, utils.ToBytesList())
 	key := utils.RandString(10)
 	pos1 := utils.RandString(10)
 	pos2 := utils.RandString(10)
-	GeoAdd(testDB, utils.ToBytesList(key,
+	execGeoAdd(testDB, utils.ToBytesList(key,
 		"13.361389", "38.115556", pos1,
 		"15.087269", "37.502669", pos2,
 	))
-	result := GeoRadius(testDB, utils.ToBytesList(key, "15", "37", "200", "km"))
+	result := execGeoRadius(testDB, utils.ToBytesList(key, "15", "37", "200", "km"))
 	asserts.AssertMultiBulkReplySize(t, result, 2)
 }
 
 func TestGeoRadiusByMember(t *testing.T) {
-	FlushDB(testDB, utils.ToBytesList())
+	execFlushDB(testDB, utils.ToBytesList())
 	key := utils.RandString(10)
 	pos1 := utils.RandString(10)
 	pos2 := utils.RandString(10)
 	pivot := utils.RandString(10)
-	GeoAdd(testDB, utils.ToBytesList(key,
+	execGeoAdd(testDB, utils.ToBytesList(key,
 		"13.361389", "38.115556", pos1,
 		"17.087269", "38.502669", pos2,
 		"13.583333", "37.316667", pivot,
 	))
-	result := GeoRadiusByMember(testDB, utils.ToBytesList(key, pivot, "100", "km"))
+	result := execGeoRadiusByMember(testDB, utils.ToBytesList(key, pivot, "100", "km"))
 	asserts.AssertMultiBulkReplySize(t, result, 2)
 }
 
 func TestGeoPos(t *testing.T) {
-	FlushDB(testDB, utils.ToBytesList())
+	execFlushDB(testDB, utils.ToBytesList())
 	key := utils.RandString(10)
 	pos1 := utils.RandString(10)
 	pos2 := utils.RandString(10)
-	GeoAdd(testDB, utils.ToBytesList(key,
+	execGeoAdd(testDB, utils.ToBytesList(key,
 		"13.361389", "38.115556", pos1,
 	))
-	result := GeoPos(testDB, utils.ToBytesList(key, pos1, pos2))
+	result := execGeoPos(testDB, utils.ToBytesList(key, pos1, pos2))
 	expected := "*2\r\n*2\r\n$18\r\n13.361386698670685\r\n$17\r\n38.11555536696687\r\n*0\r\n"
 	if string(result.ToBytes()) != expected {
 		t.Error("test failed")
@@ -63,15 +63,15 @@ func TestGeoPos(t *testing.T) {
 }
 
 func TestGeoDist(t *testing.T) {
-	FlushDB(testDB, utils.ToBytesList())
+	execFlushDB(testDB, utils.ToBytesList())
 	key := utils.RandString(10)
 	pos1 := utils.RandString(10)
 	pos2 := utils.RandString(10)
-	GeoAdd(testDB, utils.ToBytesList(key,
+	execGeoAdd(testDB, utils.ToBytesList(key,
 		"13.361389", "38.115556", pos1,
 		"15.087269", "37.502669", pos2,
 	))
-	result := GeoDist(testDB, utils.ToBytesList(key, pos1, pos2, "km"))
+	result := execGeoDist(testDB, utils.ToBytesList(key, pos1, pos2, "km"))
 	bulkReply, ok := result.(*reply.BulkReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected bulk reply, actually %s", result.ToBytes()))
@@ -86,7 +86,7 @@ func TestGeoDist(t *testing.T) {
 		t.Errorf("expected 166.274, actual: %f", dist)
 	}
 
-	result = GeoDist(testDB, utils.ToBytesList(key, pos1, pos2, "m"))
+	result = execGeoDist(testDB, utils.ToBytesList(key, pos1, pos2, "m"))
 	bulkReply, ok = result.(*reply.BulkReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected bulk reply, actually %s", result.ToBytes()))
diff --git a/hash.go b/hash.go
index cdd99c9..bf4a03c 100644
--- a/hash.go
+++ b/hash.go
@@ -36,12 +36,9 @@ func (db *DB) getOrInitDict(key string) (dict Dict.Dict, inited bool, errReply r
 	return dict, inited, nil
 }
 
-// HSet sets field in hash table
-func HSet(db *DB, args [][]byte) redis.Reply {
+// execHSet sets field in hash table
+func execHSet(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hset' command")
-	}
 	key := string(args[0])
 	field := string(args[1])
 	value := args[2]
@@ -61,12 +58,9 @@ func HSet(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(result))
 }
 
-// HSetNX sets field in hash table only if field not exists
-func HSetNX(db *DB, args [][]byte) redis.Reply {
+// execHSetNX sets field in hash table only if field not exists
+func execHSetNX(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hsetnx' command")
-	}
 	key := string(args[0])
 	field := string(args[1])
 	value := args[2]
@@ -87,12 +81,9 @@ func HSetNX(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(result))
 }
 
-// HGet gets field value of hash table
-func HGet(db *DB, args [][]byte) redis.Reply {
+// execHGet gets field value of hash table
+func execHGet(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hget' command")
-	}
 	key := string(args[0])
 	field := string(args[1])
 
@@ -116,12 +107,9 @@ func HGet(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(value)
 }
 
-// HExists checks if a hash field exists
-func HExists(db *DB, args [][]byte) redis.Reply {
+// execHExists checks if a hash field exists
+func execHExists(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hexists' command")
-	}
 	key := string(args[0])
 	field := string(args[1])
 
@@ -144,12 +132,9 @@ func HExists(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(0)
 }
 
-// HDel deletes a hash field
-func HDel(db *DB, args [][]byte) redis.Reply {
+// execHDel deletes a hash field
+func execHDel(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hdel' command")
-	}
 	key := string(args[0])
 	fields := make([]string, len(args)-1)
 	fieldArgs := args[1:]
@@ -184,12 +169,9 @@ func HDel(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(deleted))
 }
 
-// HLen gets number of fields in hash table
-func HLen(db *DB, args [][]byte) redis.Reply {
+// execHLen gets number of fields in hash table
+func execHLen(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hlen' command")
-	}
 	key := string(args[0])
 
 	db.RLock(key)
@@ -205,11 +187,11 @@ func HLen(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(dict.Len()))
 }
 
-// HMSet sets multi fields in hash table
-func HMSet(db *DB, args [][]byte) redis.Reply {
+// execHMSet sets multi fields in hash table
+func execHMSet(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) < 3 || len(args)%2 != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hmset' command")
+	if len(args)%2 != 1 {
+		return reply.MakeSyntaxErrReply()
 	}
 	key := string(args[0])
 	size := (len(args) - 1) / 2
@@ -241,9 +223,6 @@ func HMSet(db *DB, args [][]byte) redis.Reply {
 
 // HMGet gets multi fields in hash table
 func HMGet(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hmget' command")
-	}
 	key := string(args[0])
 	size := len(args) - 1
 	fields := make([]string, size)
@@ -276,11 +255,8 @@ func HMGet(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(result)
 }
 
-// HKeys gets all field names in hash table
-func HKeys(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hkeys' command")
-	}
+// execHKeys gets all field names in hash table
+func execHKeys(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	db.RLock(key)
@@ -304,11 +280,8 @@ func HKeys(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(fields[:i])
 }
 
-// HVals gets all field value in hash table
-func HVals(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hvals' command")
-	}
+// execHVals gets all field value in hash table
+func execHVals(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	db.RLock(key)
@@ -333,11 +306,8 @@ func HVals(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(values[:i])
 }
 
-// HGetAll gets all key-value entries in hash table
-func HGetAll(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hgetAll' command")
-	}
+// execHGetAll gets all key-value entries in hash table
+func execHGetAll(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	db.RLock(key)
@@ -365,11 +335,8 @@ func HGetAll(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(result[:i])
 }
 
-// HIncrBy increments the integer value of a hash field by the given number
-func HIncrBy(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hincrby' command")
-	}
+// execHIncrBy increments the integer value of a hash field by the given number
+func execHIncrBy(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	field := string(args[1])
 	rawDelta := string(args[2])
@@ -403,11 +370,8 @@ func HIncrBy(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(bytes)
 }
 
-// HIncrByFloat increments the float value of a hash field by the given number
-func HIncrByFloat(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'hincrbyfloat' command")
-	}
+// execHIncrByFloat increments the float value of a hash field by the given number
+func execHIncrByFloat(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	field := string(args[1])
 	rawDelta := string(args[2])
@@ -440,3 +404,19 @@ func HIncrByFloat(db *DB, args [][]byte) redis.Reply {
 	db.AddAof(makeAofCmd("hincrbyfloat", args))
 	return reply.MakeBulkReply(resultBytes)
 }
+
+func init() {
+	RegisterCommand("HSet", execHSet, nil, 4)
+	RegisterCommand("HSetNX", execHSetNX, nil, 4)
+	RegisterCommand("HGet", execHGet, nil, 3)
+	RegisterCommand("HExists", execHExists, nil, 3)
+	RegisterCommand("HDel", execHDel, nil, -3)
+	RegisterCommand("HLen", execHLen, nil, 2)
+	RegisterCommand("HMSet", execHMSet, nil, -4)
+	RegisterCommand("HGet", execHGet, nil, -3)
+	RegisterCommand("HKeys", execHKeys, nil, 2)
+	RegisterCommand("HVals", execHVals, nil, 2)
+	RegisterCommand("HGetAll", execHGetAll, nil, 2)
+	RegisterCommand("HIncrBy", execHIncrBy, nil, 4)
+	RegisterCommand("HIncrByFloat", execHIncrByFloat, nil, 4)
+}
diff --git a/hash_test.go b/hash_test.go
index 71bc543..ed2ec12 100644
--- a/hash_test.go
+++ b/hash_test.go
@@ -11,7 +11,7 @@ import (
 )
 
 func TestHSet(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 
 	// test hset
@@ -21,7 +21,7 @@ func TestHSet(t *testing.T) {
 		value := utils2.RandString(10)
 		field := strconv.Itoa(i)
 		values[field] = []byte(value)
-		result := HSet(testDB, utils2.ToBytesList(key, field, value))
+		result := execHSet(testDB, utils2.ToBytesList(key, field, value))
 		if intResult, _ := result.(*reply.IntReply); intResult.Code != int64(1) {
 			t.Error(fmt.Sprintf("expected %d, actually %d", 1, intResult.Code))
 		}
@@ -29,26 +29,26 @@ func TestHSet(t *testing.T) {
 
 	// test hget and hexists
 	for field, v := range values {
-		actual := HGet(testDB, utils2.ToBytesList(key, field))
+		actual := execHGet(testDB, utils2.ToBytesList(key, field))
 		expected := reply.MakeBulkReply(v)
 		if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(actual.ToBytes())))
 		}
-		actual = HExists(testDB, utils2.ToBytesList(key, field))
+		actual = execHExists(testDB, utils2.ToBytesList(key, field))
 		if intResult, _ := actual.(*reply.IntReply); intResult.Code != int64(1) {
 			t.Error(fmt.Sprintf("expected %d, actually %d", 1, intResult.Code))
 		}
 	}
 
 	// test hlen
-	actual := HLen(testDB, utils2.ToBytesList(key))
+	actual := execHLen(testDB, utils2.ToBytesList(key))
 	if intResult, _ := actual.(*reply.IntReply); intResult.Code != int64(len(values)) {
 		t.Error(fmt.Sprintf("expected %d, actually %d", len(values), intResult.Code))
 	}
 }
 
 func TestHDel(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 
 	// set values
@@ -58,25 +58,25 @@ func TestHDel(t *testing.T) {
 		value := utils2.RandString(10)
 		field := strconv.Itoa(i)
 		fields[i] = field
-		HSet(testDB, utils2.ToBytesList(key, field, value))
+		execHSet(testDB, utils2.ToBytesList(key, field, value))
 	}
 
 	// test HDel
 	args := []string{key}
 	args = append(args, fields...)
-	actual := HDel(testDB, utils2.ToBytesList(args...))
+	actual := execHDel(testDB, utils2.ToBytesList(args...))
 	if intResult, _ := actual.(*reply.IntReply); intResult.Code != int64(len(fields)) {
 		t.Error(fmt.Sprintf("expected %d, actually %d", len(fields), intResult.Code))
 	}
 
-	actual = HLen(testDB, utils2.ToBytesList(key))
+	actual = execHLen(testDB, utils2.ToBytesList(key))
 	if intResult, _ := actual.(*reply.IntReply); intResult.Code != int64(0) {
 		t.Error(fmt.Sprintf("expected %d, actually %d", 0, intResult.Code))
 	}
 }
 
 func TestHMSet(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 
 	// test hset
@@ -89,7 +89,7 @@ func TestHMSet(t *testing.T) {
 		values[i] = utils2.RandString(10)
 		setArgs = append(setArgs, fields[i], values[i])
 	}
-	result := HMSet(testDB, utils2.ToBytesList(setArgs...))
+	result := execHMSet(testDB, utils2.ToBytesList(setArgs...))
 	if _, ok := result.(*reply.OkReply); !ok {
 		t.Error(fmt.Sprintf("expected ok, actually %s", string(result.ToBytes())))
 	}
@@ -105,7 +105,7 @@ func TestHMSet(t *testing.T) {
 }
 
 func TestHGetAll(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils2.RandString(10)
 	fields := make([]string, size)
@@ -118,11 +118,11 @@ func TestHGetAll(t *testing.T) {
 		all = append(all, fields[i], value)
 		valueMap[fields[i]] = value
 		valueSet[value] = true
-		HSet(testDB, utils2.ToBytesList(key, fields[i], value))
+		execHSet(testDB, utils2.ToBytesList(key, fields[i], value))
 	}
 
 	// test HGetAll
-	result := HGetAll(testDB, utils2.ToBytesList(key))
+	result := execHGetAll(testDB, utils2.ToBytesList(key))
 	multiBulk, ok := result.(*reply.MultiBulkReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected MultiBulkReply, actually %s", string(result.ToBytes())))
@@ -144,7 +144,7 @@ func TestHGetAll(t *testing.T) {
 	}
 
 	// test HKeys
-	result = HKeys(testDB, utils2.ToBytesList(key))
+	result = execHKeys(testDB, utils2.ToBytesList(key))
 	multiBulk, ok = result.(*reply.MultiBulkReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected MultiBulkReply, actually %s", string(result.ToBytes())))
@@ -160,7 +160,7 @@ func TestHGetAll(t *testing.T) {
 	}
 
 	// test HVals
-	result = HVals(testDB, utils2.ToBytesList(key))
+	result = execHVals(testDB, utils2.ToBytesList(key))
 	multiBulk, ok = result.(*reply.MultiBulkReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected MultiBulkReply, actually %s", string(result.ToBytes())))
@@ -178,39 +178,39 @@ func TestHGetAll(t *testing.T) {
 }
 
 func TestHIncrBy(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 
 	key := utils2.RandString(10)
-	result := HIncrBy(testDB, utils2.ToBytesList(key, "a", "1"))
+	result := execHIncrBy(testDB, utils2.ToBytesList(key, "a", "1"))
 	if bulkResult, _ := result.(*reply.BulkReply); string(bulkResult.Arg) != "1" {
 		t.Error(fmt.Sprintf("expected %s, actually %s", "1", string(bulkResult.Arg)))
 	}
-	result = HIncrBy(testDB, utils2.ToBytesList(key, "a", "1"))
+	result = execHIncrBy(testDB, utils2.ToBytesList(key, "a", "1"))
 	if bulkResult, _ := result.(*reply.BulkReply); string(bulkResult.Arg) != "2" {
 		t.Error(fmt.Sprintf("expected %s, actually %s", "2", string(bulkResult.Arg)))
 	}
 
-	result = HIncrByFloat(testDB, utils2.ToBytesList(key, "b", "1.2"))
+	result = execHIncrByFloat(testDB, utils2.ToBytesList(key, "b", "1.2"))
 	if bulkResult, _ := result.(*reply.BulkReply); string(bulkResult.Arg) != "1.2" {
 		t.Error(fmt.Sprintf("expected %s, actually %s", "1.2", string(bulkResult.Arg)))
 	}
-	result = HIncrByFloat(testDB, utils2.ToBytesList(key, "b", "1.2"))
+	result = execHIncrByFloat(testDB, utils2.ToBytesList(key, "b", "1.2"))
 	if bulkResult, _ := result.(*reply.BulkReply); string(bulkResult.Arg) != "2.4" {
 		t.Error(fmt.Sprintf("expected %s, actually %s", "2.4", string(bulkResult.Arg)))
 	}
 }
 
 func TestHSetNX(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	field := utils2.RandString(10)
 	value := utils2.RandString(10)
-	result := HSetNX(testDB, utils2.ToBytesList(key, field, value))
+	result := execHSetNX(testDB, utils2.ToBytesList(key, field, value))
 	asserts.AssertIntReply(t, result, 1)
 	value2 := utils2.RandString(10)
-	result = HSetNX(testDB, utils2.ToBytesList(key, field, value2))
+	result = execHSetNX(testDB, utils2.ToBytesList(key, field, value2))
 	asserts.AssertIntReply(t, result, 0)
-	result = HGet(testDB, utils2.ToBytesList(key, field))
+	result = execHGet(testDB, utils2.ToBytesList(key, field))
 	asserts.AssertBulkReply(t, result, value)
 
 }
diff --git a/keys.go b/keys.go
index a226150..d5be7e2 100644
--- a/keys.go
+++ b/keys.go
@@ -12,11 +12,8 @@ import (
 	"time"
 )
 
-// Del removes a key from db
-func Del(db *DB, args [][]byte) redis.Reply {
-	if len(args) == 0 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'del' command")
-	}
+// execDel removes a key from db
+func execDel(db *DB, args [][]byte) redis.Reply {
 	keys := make([]string, len(args))
 	for i, v := range args {
 		keys[i] = string(v)
@@ -32,44 +29,35 @@ func Del(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(deleted))
 }
 
-// Exists checks if a is existed in db
-func Exists(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'exists' command")
+// execExists checks if a is existed in db
+func execExists(db *DB, args [][]byte) redis.Reply {
+	result := int64(0)
+	for _, arg := range args {
+		key := string(arg)
+		_, exists := db.GetEntity(key)
+		if exists {
+			result++
+		}
 	}
-	key := string(args[0])
-	_, exists := db.GetEntity(key)
-	if exists {
-		return reply.MakeIntReply(1)
-	}
-	return reply.MakeIntReply(0)
+	return reply.MakeIntReply(result)
 }
 
-// FlushDB removes all data in current db
-func FlushDB(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 0 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'flushdb' command")
-	}
+// execFlushDB removes all data in current db
+func execFlushDB(db *DB, args [][]byte) redis.Reply {
 	db.Flush()
 	db.AddAof(makeAofCmd("flushdb", args))
 	return &reply.OkReply{}
 }
 
-// FlushAll removes all data in all db
-func FlushAll(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 0 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'flushall' command")
-	}
+// execFlushAll removes all data in all db
+func execFlushAll(db *DB, args [][]byte) redis.Reply {
 	db.Flush()
 	db.AddAof(makeAofCmd("flushdb", args))
 	return &reply.OkReply{}
 }
 
-// Type returns the type of entity, including: string, list, hash, set and zset
-func Type(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'type' command")
-	}
+// execType returns the type of entity, including: string, list, hash, set and zset
+func execType(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	entity, exists := db.GetEntity(key)
 	if !exists {
@@ -90,8 +78,8 @@ func Type(db *DB, args [][]byte) redis.Reply {
 	return &reply.UnknownErrReply{}
 }
 
-// Rename a key
-func Rename(db *DB, args [][]byte) redis.Reply {
+// execRename a key
+func execRename(db *DB, args [][]byte) redis.Reply {
 	if len(args) != 2 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'rename' command")
 	}
@@ -118,11 +106,8 @@ func Rename(db *DB, args [][]byte) redis.Reply {
 	return &reply.OkReply{}
 }
 
-// RenameNx a key, only if the new key does not exist
-func RenameNx(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'renamenx' command")
-	}
+// execRenameNx a key, only if the new key does not exist
+func execRenameNx(db *DB, args [][]byte) redis.Reply {
 	src := string(args[0])
 	dest := string(args[1])
 
@@ -151,11 +136,8 @@ func RenameNx(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(1)
 }
 
-// Expire sets a key's time to live in seconds
-func Expire(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'expire' command")
-	}
+// execExpire sets a key's time to live in seconds
+func execExpire(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	ttlArg, err := strconv.ParseInt(string(args[1]), 10, 64)
@@ -175,11 +157,8 @@ func Expire(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(1)
 }
 
-// ExpireAt sets a key's expiration in unix timestamp
-func ExpireAt(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'expireat' command")
-	}
+// execExpireAt sets a key's expiration in unix timestamp
+func execExpireAt(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	raw, err := strconv.ParseInt(string(args[1]), 10, 64)
@@ -198,11 +177,8 @@ func ExpireAt(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(1)
 }
 
-// PExpire sets a key's time to live in milliseconds
-func PExpire(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'pexpire' command")
-	}
+// execPExpire sets a key's time to live in milliseconds
+func execPExpire(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	ttlArg, err := strconv.ParseInt(string(args[1]), 10, 64)
@@ -222,11 +198,8 @@ func PExpire(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(1)
 }
 
-// PExpireAt sets a key's expiration in unix timestamp specified in milliseconds
-func PExpireAt(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'pexpireat' command")
-	}
+// execPExpireAt sets a key's expiration in unix timestamp specified in milliseconds
+func execPExpireAt(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	raw, err := strconv.ParseInt(string(args[1]), 10, 64)
@@ -246,11 +219,8 @@ func PExpireAt(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(1)
 }
 
-// TTL returns a key's time to live in seconds
-func TTL(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'ttl' command")
-	}
+// execTTL returns a key's time to live in seconds
+func execTTL(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	_, exists := db.GetEntity(key)
 	if !exists {
@@ -266,11 +236,8 @@ func TTL(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(ttl / time.Second))
 }
 
-// PTTL returns a key's time to live in milliseconds
-func PTTL(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'pttl' command")
-	}
+// execPTTL returns a key's time to live in milliseconds
+func execPTTL(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	_, exists := db.GetEntity(key)
 	if !exists {
@@ -286,11 +253,8 @@ func PTTL(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(ttl / time.Millisecond))
 }
 
-// Persist removes expiration from a key
-func Persist(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'persist' command")
-	}
+// execPersist removes expiration from a key
+func execPersist(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	_, exists := db.GetEntity(key)
 	if !exists {
@@ -309,18 +273,12 @@ func Persist(db *DB, args [][]byte) redis.Reply {
 
 // BGRewriteAOF asynchronously rewrites Append-Only-File
 func BGRewriteAOF(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 0 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'bgrewriteaof' command")
-	}
 	go db.aofRewrite()
 	return reply.MakeStatusReply("Background append only file rewriting started")
 }
 
-// Keys returns all keys matching the given pattern
-func Keys(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'keys' command")
-	}
+// execKeys returns all keys matching the given pattern
+func execKeys(db *DB, args [][]byte) redis.Reply {
 	pattern := wildcard.CompilePattern(string(args[0]))
 	result := make([][]byte, 0)
 	db.data.ForEach(func(key string, val interface{}) bool {
@@ -331,3 +289,21 @@ func Keys(db *DB, args [][]byte) redis.Reply {
 	})
 	return reply.MakeMultiBulkReply(result)
 }
+
+func init() {
+	RegisterCommand("Del", execDel, nil, -2)
+	RegisterCommand("Expire", execExpire, nil, 3)
+	RegisterCommand("ExpireAt", execExpireAt, nil, 3)
+	RegisterCommand("PExpire", execPExpire, nil, 3)
+	RegisterCommand("PExpireAt", execPExpireAt, nil, 3)
+	RegisterCommand("TTL", execTTL, nil, 2)
+	RegisterCommand("PTTL", execPTTL, nil, 2)
+	RegisterCommand("Persist", execPersist, nil, 2)
+	RegisterCommand("Exists", execExists, nil, -2)
+	RegisterCommand("Type", execType, nil, 2)
+	RegisterCommand("Rename", execRename, nil, 3)
+	RegisterCommand("RenameNx", execRenameNx, nil, 3)
+	RegisterCommand("FlushDB", execFlushDB, nil, -1)
+	RegisterCommand("FlushAll", execFlushAll, nil, -1)
+	RegisterCommand("Keys", execKeys, nil, 2)
+}
diff --git a/keys_test.go b/keys_test.go
index 37b3560..16a1e26 100644
--- a/keys_test.go
+++ b/keys_test.go
@@ -11,65 +11,65 @@ import (
 )
 
 func TestExists(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	value := utils.RandString(10)
-	Set(testDB, utils.ToBytesList(key, value))
-	result := Exists(testDB, utils.ToBytesList(key))
+	execSet(testDB, utils.ToBytesList(key, value))
+	result := execExists(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, 1)
 	key = utils.RandString(10)
-	result = Exists(testDB, utils.ToBytesList(key))
+	result = execExists(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, 0)
 }
 
 func TestType(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	value := utils.RandString(10)
-	Set(testDB, utils.ToBytesList(key, value))
-	result := Type(testDB, utils.ToBytesList(key))
+	execSet(testDB, utils.ToBytesList(key, value))
+	result := execType(testDB, utils.ToBytesList(key))
 	asserts.AssertStatusReply(t, result, "string")
 
-	Del(testDB, utils.ToBytesList(key))
-	result = Type(testDB, utils.ToBytesList(key))
+	testDB.Remove(key)
+	result = execType(testDB, utils.ToBytesList(key))
 	asserts.AssertStatusReply(t, result, "none")
-	RPush(testDB, utils.ToBytesList(key, value))
-	result = Type(testDB, utils.ToBytesList(key))
+	execRPush(testDB, utils.ToBytesList(key, value))
+	result = execType(testDB, utils.ToBytesList(key))
 	asserts.AssertStatusReply(t, result, "list")
 
-	Del(testDB, utils.ToBytesList(key))
-	HSet(testDB, utils.ToBytesList(key, key, value))
-	result = Type(testDB, utils.ToBytesList(key))
+	testDB.Remove(key)
+	execHSet(testDB, utils.ToBytesList(key, key, value))
+	result = execType(testDB, utils.ToBytesList(key))
 	asserts.AssertStatusReply(t, result, "hash")
 
-	Del(testDB, utils.ToBytesList(key))
-	SAdd(testDB, utils.ToBytesList(key, value))
-	result = Type(testDB, utils.ToBytesList(key))
+	testDB.Remove(key)
+	execSAdd(testDB, utils.ToBytesList(key, value))
+	result = execType(testDB, utils.ToBytesList(key))
 	asserts.AssertStatusReply(t, result, "set")
 
-	Del(testDB, utils.ToBytesList(key))
-	ZAdd(testDB, utils.ToBytesList(key, "1", value))
-	result = Type(testDB, utils.ToBytesList(key))
+	testDB.Remove(key)
+	execZAdd(testDB, utils.ToBytesList(key, "1", value))
+	result = execType(testDB, utils.ToBytesList(key))
 	asserts.AssertStatusReply(t, result, "zset")
 }
 
 func TestRename(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	value := utils.RandString(10)
 	newKey := key + utils.RandString(2)
-	Set(testDB, utils.ToBytesList(key, value, "ex", "1000"))
-	result := Rename(testDB, utils.ToBytesList(key, newKey))
+	execSet(testDB, utils.ToBytesList(key, value, "ex", "1000"))
+	result := execRename(testDB, utils.ToBytesList(key, newKey))
 	if _, ok := result.(*reply.OkReply); !ok {
 		t.Error("expect ok")
 		return
 	}
-	result = Exists(testDB, utils.ToBytesList(key))
+	result = execExists(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, 0)
-	result = Exists(testDB, utils.ToBytesList(newKey))
+	result = execExists(testDB, utils.ToBytesList(newKey))
 	asserts.AssertIntReply(t, result, 1)
 	// check ttl
-	result = TTL(testDB, utils.ToBytesList(newKey))
+	result = execTTL(testDB, utils.ToBytesList(newKey))
 	intResult, ok := result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
@@ -82,18 +82,18 @@ func TestRename(t *testing.T) {
 }
 
 func TestRenameNx(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	value := utils.RandString(10)
 	newKey := key + utils.RandString(2)
-	Set(testDB, utils.ToBytesList(key, value, "ex", "1000"))
-	result := RenameNx(testDB, utils.ToBytesList(key, newKey))
+	execSet(testDB, utils.ToBytesList(key, value, "ex", "1000"))
+	result := execRenameNx(testDB, utils.ToBytesList(key, newKey))
 	asserts.AssertIntReply(t, result, 1)
-	result = Exists(testDB, utils.ToBytesList(key))
+	result = execExists(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, 0)
-	result = Exists(testDB, utils.ToBytesList(newKey))
+	result = execExists(testDB, utils.ToBytesList(newKey))
 	asserts.AssertIntReply(t, result, 1)
-	result = TTL(testDB, utils.ToBytesList(newKey))
+	result = execTTL(testDB, utils.ToBytesList(newKey))
 	intResult, ok := result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
@@ -106,14 +106,14 @@ func TestRenameNx(t *testing.T) {
 }
 
 func TestTTL(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	value := utils.RandString(10)
-	Set(testDB, utils.ToBytesList(key, value))
+	execSet(testDB, utils.ToBytesList(key, value))
 
-	result := Expire(testDB, utils.ToBytesList(key, "1000"))
+	result := execExpire(testDB, utils.ToBytesList(key, "1000"))
 	asserts.AssertIntReply(t, result, 1)
-	result = TTL(testDB, utils.ToBytesList(key))
+	result = execTTL(testDB, utils.ToBytesList(key))
 	intResult, ok := result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
@@ -124,14 +124,14 @@ func TestTTL(t *testing.T) {
 		return
 	}
 
-	result = Persist(testDB, utils.ToBytesList(key))
+	result = execPersist(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, 1)
-	result = TTL(testDB, utils.ToBytesList(key))
+	result = execTTL(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, -1)
 
-	result = PExpire(testDB, utils.ToBytesList(key, "1000000"))
+	result = execPExpire(testDB, utils.ToBytesList(key, "1000000"))
 	asserts.AssertIntReply(t, result, 1)
-	result = PTTL(testDB, utils.ToBytesList(key))
+	result = execPTTL(testDB, utils.ToBytesList(key))
 	intResult, ok = result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
@@ -144,15 +144,15 @@ func TestTTL(t *testing.T) {
 }
 
 func TestExpireAt(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	value := utils.RandString(10)
-	Set(testDB, utils.ToBytesList(key, value))
+	execSet(testDB, utils.ToBytesList(key, value))
 
 	expireAt := time.Now().Add(time.Minute).Unix()
-	result := ExpireAt(testDB, utils.ToBytesList(key, strconv.FormatInt(expireAt, 10)))
+	result := execExpireAt(testDB, utils.ToBytesList(key, strconv.FormatInt(expireAt, 10)))
 	asserts.AssertIntReply(t, result, 1)
-	result = TTL(testDB, utils.ToBytesList(key))
+	result = execTTL(testDB, utils.ToBytesList(key))
 	intResult, ok := result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
@@ -164,9 +164,9 @@ func TestExpireAt(t *testing.T) {
 	}
 
 	expireAt = time.Now().Add(time.Minute).Unix()
-	result = PExpireAt(testDB, utils.ToBytesList(key, strconv.FormatInt(expireAt*1000, 10)))
+	result = execPExpireAt(testDB, utils.ToBytesList(key, strconv.FormatInt(expireAt*1000, 10)))
 	asserts.AssertIntReply(t, result, 1)
-	result = TTL(testDB, utils.ToBytesList(key))
+	result = execTTL(testDB, utils.ToBytesList(key))
 	intResult, ok = result.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", result.ToBytes()))
@@ -179,17 +179,17 @@ func TestExpireAt(t *testing.T) {
 }
 
 func TestKeys(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	value := utils.RandString(10)
-	Set(testDB, utils.ToBytesList(key, value))
-	Set(testDB, utils.ToBytesList("a:"+key, value))
-	Set(testDB, utils.ToBytesList("b:"+key, value))
+	execSet(testDB, utils.ToBytesList(key, value))
+	execSet(testDB, utils.ToBytesList("a:"+key, value))
+	execSet(testDB, utils.ToBytesList("b:"+key, value))
 
-	result := Keys(testDB, utils.ToBytesList("*"))
+	result := execKeys(testDB, utils.ToBytesList("*"))
 	asserts.AssertMultiBulkReplySize(t, result, 3)
-	result = Keys(testDB, utils.ToBytesList("a:*"))
+	result = execKeys(testDB, utils.ToBytesList("a:*"))
 	asserts.AssertMultiBulkReplySize(t, result, 1)
-	result = Keys(testDB, utils.ToBytesList("?:*"))
+	result = execKeys(testDB, utils.ToBytesList("?:*"))
 	asserts.AssertMultiBulkReplySize(t, result, 2)
 }
diff --git a/list.go b/list.go
index 72e1a29..1b27ada 100644
--- a/list.go
+++ b/list.go
@@ -35,12 +35,9 @@ func (db *DB) getOrInitList(key string) (list *List.LinkedList, isNew bool, errR
 	return list, isNew, nil
 }
 
-// LIndex gets element of list at given list
-func LIndex(db *DB, args [][]byte) redis.Reply {
+// execLIndex gets element of list at given list
+func execLIndex(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'lindex' command")
-	}
 	key := string(args[0])
 	index64, err := strconv.ParseInt(string(args[1]), 10, 64)
 	if err != nil {
@@ -73,12 +70,9 @@ func LIndex(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(val)
 }
 
-// LLen gets length of list
-func LLen(db *DB, args [][]byte) redis.Reply {
+// execLLen gets length of list
+func execLLen(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'llen' command")
-	}
 	key := string(args[0])
 
 	db.RLock(key)
@@ -96,12 +90,9 @@ func LLen(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(size)
 }
 
-// LPop removes the first element of list, and return it
-func LPop(db *DB, args [][]byte) redis.Reply {
+// execLPop removes the first element of list, and return it
+func execLPop(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'lindex' command")
-	}
 	key := string(args[0])
 
 	// lock
@@ -125,11 +116,8 @@ func LPop(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(val)
 }
 
-// LPush inserts element at head of list
-func LPush(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'lpush' command")
-	}
+// execLPush inserts element at head of list
+func execLPush(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	values := args[1:]
 
@@ -152,11 +140,8 @@ func LPush(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(list.Len()))
 }
 
-// LPushX inserts element at head of list, only if list exists
-func LPushX(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'lpushx' command")
-	}
+// execLPushX inserts element at head of list, only if list exists
+func execLPushX(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	values := args[1:]
 
@@ -181,12 +166,9 @@ func LPushX(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(list.Len()))
 }
 
-// LRange gets elements of list in given range
-func LRange(db *DB, args [][]byte) redis.Reply {
+// execLRange gets elements of list in given range
+func execLRange(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'lrange' command")
-	}
 	key := string(args[0])
 	start64, err := strconv.ParseInt(string(args[1]), 10, 64)
 	if err != nil {
@@ -244,12 +226,9 @@ func LRange(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(result)
 }
 
-// LRem removes element of list at specified index
-func LRem(db *DB, args [][]byte) redis.Reply {
+// execLRem removes element of list at specified index
+func execLRem(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'lrem' command")
-	}
 	key := string(args[0])
 	count64, err := strconv.ParseInt(string(args[1]), 10, 64)
 	if err != nil {
@@ -290,12 +269,9 @@ func LRem(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(removed))
 }
 
-// LSet puts element at specified index of list
-func LSet(db *DB, args [][]byte) redis.Reply {
+// execLSet puts element at specified index of list
+func execLSet(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'lset' command")
-	}
 	key := string(args[0])
 	index64, err := strconv.ParseInt(string(args[1]), 10, 64)
 	if err != nil {
@@ -331,12 +307,9 @@ func LSet(db *DB, args [][]byte) redis.Reply {
 	return &reply.OkReply{}
 }
 
-// RPop removes last element of list then return it
-func RPop(db *DB, args [][]byte) redis.Reply {
+// execRPop removes last element of list then return it
+func execRPop(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'rpop' command")
-	}
 	key := string(args[0])
 
 	// lock
@@ -360,11 +333,8 @@ func RPop(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(val)
 }
 
-// RPopLPush pops last element of list-A then insert it to the head of list-B
-func RPopLPush(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'rpoplpush' command")
-	}
+// execRPopLPush pops last element of list-A then insert it to the head of list-B
+func execRPopLPush(db *DB, args [][]byte) redis.Reply {
 	sourceKey := string(args[0])
 	destKey := string(args[1])
 
@@ -399,12 +369,9 @@ func RPopLPush(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(val)
 }
 
-// RPush inserts element at last of list
-func RPush(db *DB, args [][]byte) redis.Reply {
+// execRPush inserts element at last of list
+func execRPush(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'rpush' command")
-	}
 	key := string(args[0])
 	values := args[1:]
 
@@ -426,8 +393,8 @@ func RPush(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(list.Len()))
 }
 
-// RPushX inserts element at last of list only if list exists
-func RPushX(db *DB, args [][]byte) redis.Reply {
+// execRPushX inserts element at last of list only if list exists
+func execRPushX(db *DB, args [][]byte) redis.Reply {
 	if len(args) < 2 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'rpush' command")
 	}
@@ -455,3 +422,18 @@ func RPushX(db *DB, args [][]byte) redis.Reply {
 
 	return reply.MakeIntReply(int64(list.Len()))
 }
+
+func init() {
+	RegisterCommand("LPush", execLPush, nil, -3)
+	RegisterCommand("LPushX", execLPushX, nil, -3)
+	RegisterCommand("RPush", execRPush, nil, -3)
+	RegisterCommand("RPushX", execRPushX, nil, -3)
+	RegisterCommand("LPop", execLPop, nil, 2)
+	RegisterCommand("RPop", execRPop, nil, 2)
+	RegisterCommand("RPopLPush", execRPopLPush, nil, 4)
+	RegisterCommand("LRem", execLRem, nil, 4)
+	RegisterCommand("LLen", execLLen, nil, 2)
+	RegisterCommand("LIndex", execLIndex, nil, 3)
+	RegisterCommand("LSet", execLSet, nil, 4)
+	RegisterCommand("LRange", execLRange, nil, 4)
+}
diff --git a/list_test.go b/list_test.go
index 4259719..0e6eaba 100644
--- a/list_test.go
+++ b/list_test.go
@@ -10,7 +10,7 @@ import (
 )
 
 func TestPush(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 
 	// rpush single
@@ -19,17 +19,17 @@ func TestPush(t *testing.T) {
 	for i := 0; i < size; i++ {
 		value := utils2.RandString(10)
 		values[i] = []byte(value)
-		result := RPush(testDB, utils2.ToBytesList(key, value))
+		result := execRPush(testDB, utils2.ToBytesList(key, value))
 		if intResult, _ := result.(*reply.IntReply); intResult.Code != int64(i+1) {
 			t.Error(fmt.Sprintf("expected %d, actually %d", i+1, intResult.Code))
 		}
 	}
-	actual := LRange(testDB, utils2.ToBytesList(key, "0", "-1"))
+	actual := execLRange(testDB, utils2.ToBytesList(key, "0", "-1"))
 	expected := reply.MakeMultiBulkReply(values)
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("push error")
 	}
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 
 	// rpush multi
 	key = utils2.RandString(10)
@@ -39,16 +39,16 @@ func TestPush(t *testing.T) {
 		value := utils2.RandString(10)
 		values[i+1] = []byte(value)
 	}
-	result := RPush(testDB, values)
+	result := execRPush(testDB, values)
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != int64(size) {
 		t.Error(fmt.Sprintf("expected %d, actually %d", size, intResult.Code))
 	}
-	actual = LRange(testDB, utils2.ToBytesList(key, "0", "-1"))
+	actual = execLRange(testDB, utils2.ToBytesList(key, "0", "-1"))
 	expected = reply.MakeMultiBulkReply(values[1:])
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("push error")
 	}
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 
 	// left push single
 	key = utils2.RandString(10)
@@ -56,17 +56,17 @@ func TestPush(t *testing.T) {
 	for i := 0; i < size; i++ {
 		value := utils2.RandString(10)
 		values[size-i-1] = []byte(value)
-		result = LPush(testDB, utils2.ToBytesList(key, value))
+		result = execLPush(testDB, utils2.ToBytesList(key, value))
 		if intResult, _ := result.(*reply.IntReply); intResult.Code != int64(i+1) {
 			t.Error(fmt.Sprintf("expected %d, actually %d", i+1, intResult.Code))
 		}
 	}
-	actual = LRange(testDB, utils2.ToBytesList(key, "0", "-1"))
+	actual = execLRange(testDB, utils2.ToBytesList(key, "0", "-1"))
 	expected = reply.MakeMultiBulkReply(values)
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("push error")
 	}
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 
 	// left push multi
 	key = utils2.RandString(10)
@@ -78,33 +78,33 @@ func TestPush(t *testing.T) {
 		values[i+1] = []byte(value)
 		expectedValues[size-i-1] = []byte(value)
 	}
-	result = LPush(testDB, values)
+	result = execLPush(testDB, values)
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != int64(size) {
 		t.Error(fmt.Sprintf("expected %d, actually %d", size, intResult.Code))
 	}
-	actual = LRange(testDB, utils2.ToBytesList(key, "0", "-1"))
+	actual = execLRange(testDB, utils2.ToBytesList(key, "0", "-1"))
 	expected = reply.MakeMultiBulkReply(expectedValues)
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("push error")
 	}
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 }
 
 func TestLRange(t *testing.T) {
 	// prepare list
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils2.RandString(10)
 	values := make([][]byte, size)
 	for i := 0; i < size; i++ {
 		value := utils2.RandString(10)
-		RPush(testDB, utils2.ToBytesList(key, value))
+		execRPush(testDB, utils2.ToBytesList(key, value))
 		values[i] = []byte(value)
 	}
 
 	start := "0"
 	end := "9"
-	actual := LRange(testDB, utils2.ToBytesList(key, start, end))
+	actual := execLRange(testDB, utils2.ToBytesList(key, start, end))
 	expected := reply.MakeMultiBulkReply(values[0:10])
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("range error [%s, %s]", start, end))
@@ -112,7 +112,7 @@ func TestLRange(t *testing.T) {
 
 	start = "0"
 	end = "200"
-	actual = LRange(testDB, utils2.ToBytesList(key, start, end))
+	actual = execLRange(testDB, utils2.ToBytesList(key, start, end))
 	expected = reply.MakeMultiBulkReply(values)
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("range error [%s, %s]", start, end))
@@ -120,7 +120,7 @@ func TestLRange(t *testing.T) {
 
 	start = "0"
 	end = "-10"
-	actual = LRange(testDB, utils2.ToBytesList(key, start, end))
+	actual = execLRange(testDB, utils2.ToBytesList(key, start, end))
 	expected = reply.MakeMultiBulkReply(values[0 : size-10+1])
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("range error [%s, %s]", start, end))
@@ -128,7 +128,7 @@ func TestLRange(t *testing.T) {
 
 	start = "0"
 	end = "-200"
-	actual = LRange(testDB, utils2.ToBytesList(key, start, end))
+	actual = execLRange(testDB, utils2.ToBytesList(key, start, end))
 	expected = reply.MakeMultiBulkReply(values[0:0])
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("range error [%s, %s]", start, end))
@@ -136,7 +136,7 @@ func TestLRange(t *testing.T) {
 
 	start = "-10"
 	end = "-1"
-	actual = LRange(testDB, utils2.ToBytesList(key, start, end))
+	actual = execLRange(testDB, utils2.ToBytesList(key, start, end))
 	expected = reply.MakeMultiBulkReply(values[90:])
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("range error [%s, %s]", start, end))
@@ -145,23 +145,23 @@ func TestLRange(t *testing.T) {
 
 func TestLIndex(t *testing.T) {
 	// prepare list
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils2.RandString(10)
 	values := make([][]byte, size)
 	for i := 0; i < size; i++ {
 		value := utils2.RandString(10)
-		RPush(testDB, utils2.ToBytesList(key, value))
+		execRPush(testDB, utils2.ToBytesList(key, value))
 		values[i] = []byte(value)
 	}
 
-	result := LLen(testDB, utils2.ToBytesList(key))
+	result := execLLen(testDB, utils2.ToBytesList(key))
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != int64(size) {
 		t.Error(fmt.Sprintf("expected %d, actually %d", size, intResult.Code))
 	}
 
 	for i := 0; i < size; i++ {
-		result = LIndex(testDB, utils2.ToBytesList(key, strconv.Itoa(i)))
+		result = execLIndex(testDB, utils2.ToBytesList(key, strconv.Itoa(i)))
 		expected := reply.MakeBulkReply(values[i])
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -169,7 +169,7 @@ func TestLIndex(t *testing.T) {
 	}
 
 	for i := 1; i <= size; i++ {
-		result = LIndex(testDB, utils2.ToBytesList(key, strconv.Itoa(-i)))
+		result = execLIndex(testDB, utils2.ToBytesList(key, strconv.Itoa(-i)))
 		expected := reply.MakeBulkReply(values[size-i])
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -179,55 +179,55 @@ func TestLIndex(t *testing.T) {
 
 func TestLRem(t *testing.T) {
 	// prepare list
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	values := []string{key, "a", "b", "a", "a", "c", "a", "a"}
-	RPush(testDB, utils2.ToBytesList(values...))
+	execRPush(testDB, utils2.ToBytesList(values...))
 
-	result := LRem(testDB, utils2.ToBytesList(key, "1", "a"))
+	result := execLRem(testDB, utils2.ToBytesList(key, "1", "a"))
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != 1 {
 		t.Error(fmt.Sprintf("expected %d, actually %d", 1, intResult.Code))
 	}
-	result = LLen(testDB, utils2.ToBytesList(key))
+	result = execLLen(testDB, utils2.ToBytesList(key))
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != 6 {
 		t.Error(fmt.Sprintf("expected %d, actually %d", 6, intResult.Code))
 	}
 
-	result = LRem(testDB, utils2.ToBytesList(key, "-2", "a"))
+	result = execLRem(testDB, utils2.ToBytesList(key, "-2", "a"))
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != 2 {
 		t.Error(fmt.Sprintf("expected %d, actually %d", 2, intResult.Code))
 	}
-	result = LLen(testDB, utils2.ToBytesList(key))
+	result = execLLen(testDB, utils2.ToBytesList(key))
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != 4 {
 		t.Error(fmt.Sprintf("expected %d, actually %d", 4, intResult.Code))
 	}
 
-	result = LRem(testDB, utils2.ToBytesList(key, "0", "a"))
+	result = execLRem(testDB, utils2.ToBytesList(key, "0", "a"))
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != 2 {
 		t.Error(fmt.Sprintf("expected %d, actually %d", 2, intResult.Code))
 	}
-	result = LLen(testDB, utils2.ToBytesList(key))
+	result = execLLen(testDB, utils2.ToBytesList(key))
 	if intResult, _ := result.(*reply.IntReply); intResult.Code != 2 {
 		t.Error(fmt.Sprintf("expected %d, actually %d", 2, intResult.Code))
 	}
 }
 
 func TestLSet(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	values := []string{key, "a", "b", "c", "d", "e", "f"}
-	RPush(testDB, utils2.ToBytesList(values...))
+	execRPush(testDB, utils2.ToBytesList(values...))
 
 	// test positive index
 	size := len(values) - 1
 	for i := 0; i < size; i++ {
 		indexStr := strconv.Itoa(i)
 		value := utils2.RandString(10)
-		result := LSet(testDB, utils2.ToBytesList(key, indexStr, value))
+		result := execLSet(testDB, utils2.ToBytesList(key, indexStr, value))
 		if _, ok := result.(*reply.OkReply); !ok {
 			t.Error(fmt.Sprintf("expected OK, actually %s", string(result.ToBytes())))
 		}
-		result = LIndex(testDB, utils2.ToBytesList(key, indexStr))
+		result = execLIndex(testDB, utils2.ToBytesList(key, indexStr))
 		expected := reply.MakeBulkReply([]byte(value))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -236,11 +236,11 @@ func TestLSet(t *testing.T) {
 	// test negative index
 	for i := 1; i <= size; i++ {
 		value := utils2.RandString(10)
-		result := LSet(testDB, utils2.ToBytesList(key, strconv.Itoa(-i), value))
+		result := execLSet(testDB, utils2.ToBytesList(key, strconv.Itoa(-i), value))
 		if _, ok := result.(*reply.OkReply); !ok {
 			t.Error(fmt.Sprintf("expected OK, actually %s", string(result.ToBytes())))
 		}
-		result = LIndex(testDB, utils2.ToBytesList(key, strconv.Itoa(len(values)-i-1)))
+		result = execLIndex(testDB, utils2.ToBytesList(key, strconv.Itoa(len(values)-i-1)))
 		expected := reply.MakeBulkReply([]byte(value))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -249,16 +249,16 @@ func TestLSet(t *testing.T) {
 
 	// test illegal index
 	value := utils2.RandString(10)
-	result := LSet(testDB, utils2.ToBytesList(key, strconv.Itoa(-len(values)-1), value))
+	result := execLSet(testDB, utils2.ToBytesList(key, strconv.Itoa(-len(values)-1), value))
 	expected := reply.MakeErrReply("ERR index out of range")
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 	}
-	result = LSet(testDB, utils2.ToBytesList(key, strconv.Itoa(len(values)), value))
+	result = execLSet(testDB, utils2.ToBytesList(key, strconv.Itoa(len(values)), value))
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 	}
-	result = LSet(testDB, utils2.ToBytesList(key, "a", value))
+	result = execLSet(testDB, utils2.ToBytesList(key, "a", value))
 	expected = reply.MakeErrReply("ERR value is not an integer or out of range")
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -266,20 +266,20 @@ func TestLSet(t *testing.T) {
 }
 
 func TestLPop(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	values := []string{key, "a", "b", "c", "d", "e", "f"}
-	RPush(testDB, utils2.ToBytesList(values...))
+	execRPush(testDB, utils2.ToBytesList(values...))
 	size := len(values) - 1
 
 	for i := 0; i < size; i++ {
-		result := LPop(testDB, utils2.ToBytesList(key))
+		result := execLPop(testDB, utils2.ToBytesList(key))
 		expected := reply.MakeBulkReply([]byte(values[i+1]))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 		}
 	}
-	result := RPop(testDB, utils2.ToBytesList(key))
+	result := execRPop(testDB, utils2.ToBytesList(key))
 	expected := &reply.NullBulkReply{}
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -287,20 +287,20 @@ func TestLPop(t *testing.T) {
 }
 
 func TestRPop(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	values := []string{key, "a", "b", "c", "d", "e", "f"}
-	RPush(testDB, utils2.ToBytesList(values...))
+	execRPush(testDB, utils2.ToBytesList(values...))
 	size := len(values) - 1
 
 	for i := 0; i < size; i++ {
-		result := RPop(testDB, utils2.ToBytesList(key))
+		result := execRPop(testDB, utils2.ToBytesList(key))
 		expected := reply.MakeBulkReply([]byte(values[len(values)-i-1]))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 		}
 	}
-	result := RPop(testDB, utils2.ToBytesList(key))
+	result := execRPop(testDB, utils2.ToBytesList(key))
 	expected := &reply.NullBulkReply{}
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -308,25 +308,25 @@ func TestRPop(t *testing.T) {
 }
 
 func TestRPopLPush(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key1 := utils2.RandString(10)
 	key2 := utils2.RandString(10)
 	values := []string{key1, "a", "b", "c", "d", "e", "f"}
-	RPush(testDB, utils2.ToBytesList(values...))
+	execRPush(testDB, utils2.ToBytesList(values...))
 	size := len(values) - 1
 
 	for i := 0; i < size; i++ {
-		result := RPopLPush(testDB, utils2.ToBytesList(key1, key2))
+		result := execRPopLPush(testDB, utils2.ToBytesList(key1, key2))
 		expected := reply.MakeBulkReply([]byte(values[len(values)-i-1]))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 		}
-		result = LIndex(testDB, utils2.ToBytesList(key2, "0"))
+		result = execLIndex(testDB, utils2.ToBytesList(key2, "0"))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 		}
 	}
-	result := RPop(testDB, utils2.ToBytesList(key1))
+	result := execRPop(testDB, utils2.ToBytesList(key1))
 	expected := &reply.NullBulkReply{}
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
@@ -334,23 +334,23 @@ func TestRPopLPush(t *testing.T) {
 }
 
 func TestRPushX(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
-	result := RPushX(testDB, utils2.ToBytesList(key, "1"))
+	result := execRPushX(testDB, utils2.ToBytesList(key, "1"))
 	expected := reply.MakeIntReply(int64(0))
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 	}
 
-	RPush(testDB, utils2.ToBytesList(key, "1"))
+	execRPush(testDB, utils2.ToBytesList(key, "1"))
 	for i := 0; i < 10; i++ {
 		value := utils2.RandString(10)
-		result := RPushX(testDB, utils2.ToBytesList(key, value))
+		result := execRPushX(testDB, utils2.ToBytesList(key, value))
 		expected := reply.MakeIntReply(int64(i + 2))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 		}
-		result = LIndex(testDB, utils2.ToBytesList(key, "-1"))
+		result = execLIndex(testDB, utils2.ToBytesList(key, "-1"))
 		expected2 := reply.MakeBulkReply([]byte(value))
 		if !utils.BytesEquals(result.ToBytes(), expected2.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected2.ToBytes()), string(result.ToBytes())))
@@ -359,23 +359,23 @@ func TestRPushX(t *testing.T) {
 }
 
 func TestLPushX(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
-	result := RPushX(testDB, utils2.ToBytesList(key, "1"))
+	result := execRPushX(testDB, utils2.ToBytesList(key, "1"))
 	expected := reply.MakeIntReply(int64(0))
 	if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 		t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 	}
 
-	LPush(testDB, utils2.ToBytesList(key, "1"))
+	execLPush(testDB, utils2.ToBytesList(key, "1"))
 	for i := 0; i < 10; i++ {
 		value := utils2.RandString(10)
-		result := LPushX(testDB, utils2.ToBytesList(key, value))
+		result := execLPushX(testDB, utils2.ToBytesList(key, value))
 		expected := reply.MakeIntReply(int64(i + 2))
 		if !utils.BytesEquals(result.ToBytes(), expected.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected.ToBytes()), string(result.ToBytes())))
 		}
-		result = LIndex(testDB, utils2.ToBytesList(key, "0"))
+		result = execLIndex(testDB, utils2.ToBytesList(key, "0"))
 		expected2 := reply.MakeBulkReply([]byte(value))
 		if !utils.BytesEquals(result.ToBytes(), expected2.ToBytes()) {
 			t.Error(fmt.Sprintf("expected %s, actually %s", string(expected2.ToBytes()), string(result.ToBytes())))
diff --git a/prepare.go b/prepare.go
new file mode 100644
index 0000000..4de41bc
--- /dev/null
+++ b/prepare.go
@@ -0,0 +1,5 @@
+package godis
+
+func noPre(args [][]byte) ([]string, [][][]byte) {
+	return nil, nil
+}
diff --git a/redis/reply/errors.go b/redis/reply/errors.go
index 12b19fe..40f2734 100644
--- a/redis/reply/errors.go
+++ b/redis/reply/errors.go
@@ -28,10 +28,23 @@ func (r *ArgNumErrReply) Error() string {
 	return "ERR wrong number of arguments for '" + r.Cmd + "' command"
 }
 
+// MakeArgNumErrReply represents wrong number of arguments for command
+func MakeArgNumErrReply(cmd string) *ArgNumErrReply {
+	return &ArgNumErrReply{
+		Cmd: cmd,
+	}
+}
+
 // SyntaxErrReply represents meeting unexpected arguments
 type SyntaxErrReply struct{}
 
 var syntaxErrBytes = []byte("-Err syntax error\r\n")
+var theSyntaxErrReply = &SyntaxErrReply{}
+
+// MakeSyntaxErrReply creates syntax error
+func MakeSyntaxErrReply() *SyntaxErrReply {
+	return theSyntaxErrReply
+}
 
 // ToBytes marshals redis.Reply
 func (r *SyntaxErrReply) ToBytes() []byte {
diff --git a/router.go b/router.go
index 56636c2..3f63491 100644
--- a/router.go
+++ b/router.go
@@ -1,102 +1,23 @@
 package godis
 
-func makeRouter() map[string]cmdFunc {
-	routerMap := make(map[string]cmdFunc)
-	routerMap["ping"] = Ping
+import "strings"
 
-	routerMap["del"] = Del
-	routerMap["expire"] = Expire
-	routerMap["expireat"] = ExpireAt
-	routerMap["pexpire"] = PExpire
-	routerMap["pexpireat"] = PExpireAt
-	routerMap["ttl"] = TTL
-	routerMap["pttl"] = PTTL
-	routerMap["persist"] = Persist
-	routerMap["exists"] = Exists
-	routerMap["type"] = Type
-	routerMap["rename"] = Rename
-	routerMap["renamenx"] = RenameNx
+var cmdTable = make(map[string]*command)
 
-	routerMap["set"] = Set
-	routerMap["setnx"] = SetNX
-	routerMap["setex"] = SetEX
-	routerMap["psetex"] = PSetEX
-	routerMap["mset"] = MSet
-	routerMap["mget"] = MGet
-	routerMap["msetnx"] = MSetNX
-	routerMap["get"] = Get
-	routerMap["getset"] = GetSet
-	routerMap["incr"] = Incr
-	routerMap["incrby"] = IncrBy
-	routerMap["incrbyfloat"] = IncrByFloat
-	routerMap["decr"] = Decr
-	routerMap["decrby"] = DecrBy
-
-	routerMap["lpush"] = LPush
-	routerMap["lpushx"] = LPushX
-	routerMap["rpush"] = RPush
-	routerMap["rpushx"] = RPushX
-	routerMap["lpop"] = LPop
-	routerMap["rpop"] = RPop
-	routerMap["rpoplpush"] = RPopLPush
-	routerMap["lrem"] = LRem
-	routerMap["llen"] = LLen
-	routerMap["lindex"] = LIndex
-	routerMap["lset"] = LSet
-	routerMap["lrange"] = LRange
-
-	routerMap["hset"] = HSet
-	routerMap["hsetnx"] = HSetNX
-	routerMap["hget"] = HGet
-	routerMap["hexists"] = HExists
-	routerMap["hdel"] = HDel
-	routerMap["hlen"] = HLen
-	routerMap["hmget"] = HMGet
-	routerMap["hmset"] = HMSet
-	routerMap["hkeys"] = HKeys
-	routerMap["hvals"] = HVals
-	routerMap["hgetall"] = HGetAll
-	routerMap["hincrby"] = HIncrBy
-	routerMap["hincrbyfloat"] = HIncrByFloat
-
-	routerMap["sadd"] = SAdd
-	routerMap["sismember"] = SIsMember
-	routerMap["srem"] = SRem
-	routerMap["scard"] = SCard
-	routerMap["smembers"] = SMembers
-	routerMap["sinter"] = SInter
-	routerMap["sinterstore"] = SInterStore
-	routerMap["sunion"] = SUnion
-	routerMap["sunionstore"] = SUnionStore
-	routerMap["sdiff"] = SDiff
-	routerMap["sdiffstore"] = SDiffStore
-	routerMap["srandmember"] = SRandMember
-
-	routerMap["zadd"] = ZAdd
-	routerMap["zscore"] = ZScore
-	routerMap["zincrby"] = ZIncrBy
-	routerMap["zrank"] = ZRank
-	routerMap["zcount"] = ZCount
-	routerMap["zrevrank"] = ZRevRank
-	routerMap["zcard"] = ZCard
-	routerMap["zrange"] = ZRange
-	routerMap["zrevrange"] = ZRevRange
-	routerMap["zrangebyscore"] = ZRangeByScore
-	routerMap["zrevrangebyscore"] = ZRevRangeByScore
-	routerMap["zrem"] = ZRem
-	routerMap["zremrangebyscore"] = ZRemRangeByScore
-	routerMap["zremrangebyrank"] = ZRemRangeByRank
-
-	routerMap["geoadd"] = GeoAdd
-	routerMap["geopos"] = GeoPos
-	routerMap["geodist"] = GeoDist
-	routerMap["geohash"] = GeoHash
-	routerMap["georadius"] = GeoRadius
-	routerMap["georadiusbymember"] = GeoRadiusByMember
-
-	routerMap["flushdb"] = FlushDB
-	routerMap["flushall"] = FlushAll
-	routerMap["keys"] = Keys
-
-	return routerMap
+type command struct {
+	executor ExecFunc
+	prepare  PreFunc // return related keys and rollback command
+	arity    int     // allow number of args, arity < 0 means len(args) >= -arity
+}
+
+// RegisterCommand registers a new command
+// arity means allowed number of cmdArgs, arity < 0 means len(args) >= -arity.
+// for example: the arity of `get` is 2, `mget` is -2
+func RegisterCommand(name string, executor ExecFunc, prepare PreFunc, arity int) {
+	name = strings.ToLower(name)
+	cmdTable[name] = &command{
+		executor: executor,
+		prepare:  prepare,
+		arity:    arity,
+	}
 }
diff --git a/server.go b/server.go
index 16eacd5..8e518b3 100644
--- a/server.go
+++ b/server.go
@@ -39,3 +39,7 @@ func isAuthenticated(c redis.Connection) bool {
 	}
 	return c.GetPassword() == config.Properties.RequirePass
 }
+
+func init() {
+	RegisterCommand("ping", Ping, nil, -1)
+}
diff --git a/server_test.go b/server_test.go
index ca1bb1e..291cadc 100644
--- a/server_test.go
+++ b/server_test.go
@@ -21,18 +21,20 @@ func TestPing(t *testing.T) {
 func TestAuth(t *testing.T) {
 	passwd := utils.RandString(10)
 	c := &connection.FakeConn{}
-	ret := Auth(testDB, c, utils.ToBytesList())
+	ret := testDB.Exec(c, utils.ToBytesList("AUTH"))
 	asserts.AssertErrReply(t, ret, "ERR wrong number of arguments for 'auth' command")
-	ret = Auth(testDB, c, utils.ToBytesList(passwd))
+	ret = testDB.Exec(c, utils.ToBytesList("AUTH", passwd))
 	asserts.AssertErrReply(t, ret, "ERR Client sent AUTH, but no password is set")
 
 	config.Properties.RequirePass = passwd
 	defer func() {
 		config.Properties.RequirePass = ""
 	}()
-	ret = Auth(testDB, c, utils.ToBytesList(passwd+passwd))
+	ret = testDB.Exec(c, utils.ToBytesList("AUTH", passwd+"wrong"))
 	asserts.AssertErrReply(t, ret, "ERR invalid password")
-	ret = Auth(testDB, c, utils.ToBytesList(passwd))
+	ret = testDB.Exec(c, utils.ToBytesList("PING"))
+	asserts.AssertErrReply(t, ret, "NOAUTH Authentication required")
+	ret = testDB.Exec(c, utils.ToBytesList("AUTH", passwd))
 	asserts.AssertStatusReply(t, ret, "OK")
 
 }
diff --git a/set.go b/set.go
index a40b5cc..0a2b449 100644
--- a/set.go
+++ b/set.go
@@ -35,11 +35,8 @@ func (db *DB) getOrInitSet(key string) (set *HashSet.Set, inited bool, errReply
 	return set, inited, nil
 }
 
-// SAdd adds members into set
-func SAdd(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sadd' command")
-	}
+// execSAdd adds members into set
+func execSAdd(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	members := args[1:]
 
@@ -60,11 +57,8 @@ func SAdd(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(counter))
 }
 
-// SIsMember checks if the given value is member of set
-func SIsMember(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sismember' command")
-	}
+// execSIsMember checks if the given value is member of set
+func execSIsMember(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	member := string(args[1])
 
@@ -87,11 +81,8 @@ func SIsMember(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(0)
 }
 
-// SRem removes a member from set
-func SRem(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'srem' command")
-	}
+// execSRem removes a member from set
+func execSRem(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	members := args[1:]
 
@@ -119,11 +110,8 @@ func SRem(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(counter))
 }
 
-// SCard gets the number of members in a set
-func SCard(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'scard' command")
-	}
+// execSCard gets the number of members in a set
+func execSCard(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	db.RLock(key)
@@ -140,11 +128,8 @@ func SCard(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(set.Len()))
 }
 
-// SMembers gets all members in a set
-func SMembers(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'smembers' command")
-	}
+// execSMembers gets all members in a set
+func execSMembers(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	// lock
@@ -170,11 +155,8 @@ func SMembers(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(arr)
 }
 
-// SInter intersect multiple sets
-func SInter(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sinter' command")
-	}
+// execSInter intersect multiple sets
+func execSInter(db *DB, args [][]byte) redis.Reply {
 	keys := make([]string, len(args))
 	for i, arg := range args {
 		keys[i] = string(arg)
@@ -216,11 +198,8 @@ func SInter(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(arr)
 }
 
-// SInterStore intersects multiple sets and store the result in a key
-func SInterStore(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sinterstore' command")
-	}
+// execSInterStore intersects multiple sets and store the result in a key
+func execSInterStore(db *DB, args [][]byte) redis.Reply {
 	dest := string(args[0])
 	keys := make([]string, len(args)-1)
 	keyArgs := args[1:]
@@ -267,11 +246,8 @@ func SInterStore(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(set.Len()))
 }
 
-// SUnion adds multiple sets
-func SUnion(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sunion' command")
-	}
+// execSUnion adds multiple sets
+func execSUnion(db *DB, args [][]byte) redis.Reply {
 	keys := make([]string, len(args))
 	for i, arg := range args {
 		keys[i] = string(arg)
@@ -313,11 +289,8 @@ func SUnion(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(arr)
 }
 
-// SUnionStore adds multiple sets and store the result in a key
-func SUnionStore(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sunionstore' command")
-	}
+// execSUnionStore adds multiple sets and store the result in a key
+func execSUnionStore(db *DB, args [][]byte) redis.Reply {
 	dest := string(args[0])
 	keys := make([]string, len(args)-1)
 	keyArgs := args[1:]
@@ -364,11 +337,8 @@ func SUnionStore(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(set.Len()))
 }
 
-// SDiff subtracts multiple sets
-func SDiff(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sdiff' command")
-	}
+// execSDiff subtracts multiple sets
+func execSDiff(db *DB, args [][]byte) redis.Reply {
 	keys := make([]string, len(args))
 	for i, arg := range args {
 		keys[i] = string(arg)
@@ -417,11 +387,8 @@ func SDiff(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(arr)
 }
 
-// SDiffStore subtracts multiple sets and store the result in a key
-func SDiffStore(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'sdiffstore' command")
-	}
+// execSDiffStore subtracts multiple sets and store the result in a key
+func execSDiffStore(db *DB, args [][]byte) redis.Reply {
 	dest := string(args[0])
 	keys := make([]string, len(args)-1)
 	keyArgs := args[1:]
@@ -477,8 +444,8 @@ func SDiffStore(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(set.Len()))
 }
 
-// SRandMember gets random members from set
-func SRandMember(db *DB, args [][]byte) redis.Reply {
+// execSRandMember gets random members from set
+func execSRandMember(db *DB, args [][]byte) redis.Reply {
 	if len(args) != 1 && len(args) != 2 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'srandmember' command")
 	}
@@ -522,3 +489,18 @@ func SRandMember(db *DB, args [][]byte) redis.Reply {
 	}
 	return &reply.EmptyMultiBulkReply{}
 }
+
+func init() {
+	RegisterCommand("SAdd", execSAdd, nil, -3)
+	RegisterCommand("SIsMember", execSIsMember, nil, 3)
+	RegisterCommand("SRem", execSRem, nil, -3)
+	RegisterCommand("SCard", execSCard, nil, 2)
+	RegisterCommand("SMembers", execSMembers, nil, 2)
+	RegisterCommand("SInter", execSInter, nil, -2)
+	RegisterCommand("SInterStore", execSInterStore, nil, -3)
+	RegisterCommand("SUnion", execSUnion, nil, -2)
+	RegisterCommand("SUnionStore", execSUnionStore, nil, -3)
+	RegisterCommand("SDiff", execSDiff, nil, -2)
+	RegisterCommand("SDiffStore", execSDiffStore, nil, -3)
+	RegisterCommand("SRandMember", execSRandMember, nil, -2)
+}
diff --git a/set_test.go b/set_test.go
index 2683fc7..820cace 100644
--- a/set_test.go
+++ b/set_test.go
@@ -11,29 +11,29 @@ import (
 
 // basic add get and remove
 func TestSAdd(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 
 	// test sadd
 	key := utils.RandString(10)
 	for i := 0; i < size; i++ {
 		member := strconv.Itoa(i)
-		result := SAdd(testDB, utils.ToBytesList(key, member))
+		result := execSAdd(testDB, utils.ToBytesList(key, member))
 		asserts.AssertIntReply(t, result, 1)
 	}
 	// test scard
-	result := SCard(testDB, utils.ToBytesList(key))
+	result := execSCard(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, size)
 
 	// test is member
 	for i := 0; i < size; i++ {
 		member := strconv.Itoa(i)
-		result := SIsMember(testDB, utils.ToBytesList(key, member))
+		result := execSIsMember(testDB, utils.ToBytesList(key, member))
 		asserts.AssertIntReply(t, result, 1)
 	}
 
 	// test members
-	result = SMembers(testDB, utils.ToBytesList(key))
+	result = execSMembers(testDB, utils.ToBytesList(key))
 	multiBulk, ok := result.(*reply.MultiBulkReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected bulk reply, actually %s", result.ToBytes()))
@@ -46,25 +46,25 @@ func TestSAdd(t *testing.T) {
 }
 
 func TestSRem(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 
 	// mock data
 	key := utils.RandString(10)
 	for i := 0; i < size; i++ {
 		member := strconv.Itoa(i)
-		SAdd(testDB, utils.ToBytesList(key, member))
+		execSAdd(testDB, utils.ToBytesList(key, member))
 	}
 	for i := 0; i < size; i++ {
 		member := strconv.Itoa(i)
-		SRem(testDB, utils.ToBytesList(key, member))
-		result := SIsMember(testDB, utils.ToBytesList(key, member))
+		execSRem(testDB, utils.ToBytesList(key, member))
+		result := execSIsMember(testDB, utils.ToBytesList(key, member))
 		asserts.AssertIntReply(t, result, 0)
 	}
 }
 
 func TestSInter(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	step := 10
 
@@ -75,39 +75,39 @@ func TestSInter(t *testing.T) {
 		keys = append(keys, key)
 		for j := start; j < size+start; j++ {
 			member := strconv.Itoa(j)
-			SAdd(testDB, utils.ToBytesList(key, member))
+			execSAdd(testDB, utils.ToBytesList(key, member))
 		}
 		start += step
 	}
-	result := SInter(testDB, utils.ToBytesList(keys...))
+	result := execSInter(testDB, utils.ToBytesList(keys...))
 	asserts.AssertMultiBulkReplySize(t, result, 70)
 
 	destKey := utils.RandString(10)
 	keysWithDest := []string{destKey}
 	keysWithDest = append(keysWithDest, keys...)
-	result = SInterStore(testDB, utils.ToBytesList(keysWithDest...))
+	result = execSInterStore(testDB, utils.ToBytesList(keysWithDest...))
 	asserts.AssertIntReply(t, result, 70)
 
 	// test empty set
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key0 := utils.RandString(10)
-	Del(testDB, utils.ToBytesList(key0))
+	testDB.Remove(key0)
 	key1 := utils.RandString(10)
-	SAdd(testDB, utils.ToBytesList(key1, "a", "b"))
+	execSAdd(testDB, utils.ToBytesList(key1, "a", "b"))
 	key2 := utils.RandString(10)
-	SAdd(testDB, utils.ToBytesList(key2, "1", "2"))
-	result = SInter(testDB, utils.ToBytesList(key0, key1, key2))
+	execSAdd(testDB, utils.ToBytesList(key2, "1", "2"))
+	result = execSInter(testDB, utils.ToBytesList(key0, key1, key2))
 	asserts.AssertMultiBulkReplySize(t, result, 0)
-	result = SInter(testDB, utils.ToBytesList(key1, key2))
+	result = execSInter(testDB, utils.ToBytesList(key1, key2))
 	asserts.AssertMultiBulkReplySize(t, result, 0)
-	result = SInterStore(testDB, utils.ToBytesList(utils.RandString(10), key0, key1, key2))
+	result = execSInterStore(testDB, utils.ToBytesList(utils.RandString(10), key0, key1, key2))
 	asserts.AssertIntReply(t, result, 0)
-	result = SInterStore(testDB, utils.ToBytesList(utils.RandString(10), key1, key2))
+	result = execSInterStore(testDB, utils.ToBytesList(utils.RandString(10), key1, key2))
 	asserts.AssertIntReply(t, result, 0)
 }
 
 func TestSUnion(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	step := 10
 
@@ -118,22 +118,22 @@ func TestSUnion(t *testing.T) {
 		keys = append(keys, key)
 		for j := start; j < size+start; j++ {
 			member := strconv.Itoa(j)
-			SAdd(testDB, utils.ToBytesList(key, member))
+			execSAdd(testDB, utils.ToBytesList(key, member))
 		}
 		start += step
 	}
-	result := SUnion(testDB, utils.ToBytesList(keys...))
+	result := execSUnion(testDB, utils.ToBytesList(keys...))
 	asserts.AssertMultiBulkReplySize(t, result, 130)
 
 	destKey := utils.RandString(10)
 	keysWithDest := []string{destKey}
 	keysWithDest = append(keysWithDest, keys...)
-	result = SUnionStore(testDB, utils.ToBytesList(keysWithDest...))
+	result = execSUnionStore(testDB, utils.ToBytesList(keysWithDest...))
 	asserts.AssertIntReply(t, result, 130)
 }
 
 func TestSDiff(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	step := 20
 
@@ -144,52 +144,52 @@ func TestSDiff(t *testing.T) {
 		keys = append(keys, key)
 		for j := start; j < size+start; j++ {
 			member := strconv.Itoa(j)
-			SAdd(testDB, utils.ToBytesList(key, member))
+			execSAdd(testDB, utils.ToBytesList(key, member))
 		}
 		start += step
 	}
-	result := SDiff(testDB, utils.ToBytesList(keys...))
+	result := execSDiff(testDB, utils.ToBytesList(keys...))
 	asserts.AssertMultiBulkReplySize(t, result, step)
 
 	destKey := utils.RandString(10)
 	keysWithDest := []string{destKey}
 	keysWithDest = append(keysWithDest, keys...)
-	result = SDiffStore(testDB, utils.ToBytesList(keysWithDest...))
+	result = execSDiffStore(testDB, utils.ToBytesList(keysWithDest...))
 	asserts.AssertIntReply(t, result, step)
 
 	// test empty set
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key0 := utils.RandString(10)
-	Del(testDB, utils.ToBytesList(key0))
+	testDB.Remove(key0)
 	key1 := utils.RandString(10)
-	SAdd(testDB, utils.ToBytesList(key1, "a", "b"))
+	execSAdd(testDB, utils.ToBytesList(key1, "a", "b"))
 	key2 := utils.RandString(10)
-	SAdd(testDB, utils.ToBytesList(key2, "a", "b"))
-	result = SDiff(testDB, utils.ToBytesList(key0, key1, key2))
+	execSAdd(testDB, utils.ToBytesList(key2, "a", "b"))
+	result = execSDiff(testDB, utils.ToBytesList(key0, key1, key2))
 	asserts.AssertMultiBulkReplySize(t, result, 0)
-	result = SDiff(testDB, utils.ToBytesList(key1, key2))
+	result = execSDiff(testDB, utils.ToBytesList(key1, key2))
 	asserts.AssertMultiBulkReplySize(t, result, 0)
-	result = SDiffStore(testDB, utils.ToBytesList(utils.RandString(10), key0, key1, key2))
+	result = execSDiffStore(testDB, utils.ToBytesList(utils.RandString(10), key0, key1, key2))
 	asserts.AssertIntReply(t, result, 0)
-	result = SDiffStore(testDB, utils.ToBytesList(utils.RandString(10), key1, key2))
+	result = execSDiffStore(testDB, utils.ToBytesList(utils.RandString(10), key1, key2))
 	asserts.AssertIntReply(t, result, 0)
 }
 
 func TestSRandMember(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
 	for j := 0; j < 100; j++ {
 		member := strconv.Itoa(j)
-		SAdd(testDB, utils.ToBytesList(key, member))
+		execSAdd(testDB, utils.ToBytesList(key, member))
 	}
-	result := SRandMember(testDB, utils.ToBytesList(key))
+	result := execSRandMember(testDB, utils.ToBytesList(key))
 	br, ok := result.(*reply.BulkReply)
 	if !ok && len(br.Arg) > 0 {
 		t.Error(fmt.Sprintf("expected bulk reply, actually %s", result.ToBytes()))
 		return
 	}
 
-	result = SRandMember(testDB, utils.ToBytesList(key, "10"))
+	result = execSRandMember(testDB, utils.ToBytesList(key, "10"))
 	asserts.AssertMultiBulkReplySize(t, result, 10)
 	multiBulk, ok := result.(*reply.MultiBulkReply)
 	if !ok {
@@ -205,12 +205,12 @@ func TestSRandMember(t *testing.T) {
 		return
 	}
 
-	result = SRandMember(testDB, utils.ToBytesList(key, "110"))
+	result = execSRandMember(testDB, utils.ToBytesList(key, "110"))
 	asserts.AssertMultiBulkReplySize(t, result, 100)
 
-	result = SRandMember(testDB, utils.ToBytesList(key, "-10"))
+	result = execSRandMember(testDB, utils.ToBytesList(key, "-10"))
 	asserts.AssertMultiBulkReplySize(t, result, 10)
 
-	result = SRandMember(testDB, utils.ToBytesList(key, "-110"))
+	result = execSRandMember(testDB, utils.ToBytesList(key, "-110"))
 	asserts.AssertMultiBulkReplySize(t, result, 110)
 }
diff --git a/sortedset.go b/sortedset.go
index 34b1606..687c842 100644
--- a/sortedset.go
+++ b/sortedset.go
@@ -36,10 +36,10 @@ func (db *DB) getOrInitSortedSet(key string) (sortedSet *SortedSet.SortedSet, in
 	return sortedSet, inited, nil
 }
 
-// ZAdd adds member into sorted set
-func ZAdd(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 3 || len(args)%2 != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zadd' command")
+// execZAdd adds member into sorted set
+func execZAdd(db *DB, args [][]byte) redis.Reply {
+	if len(args)%2 != 1 {
+		return reply.MakeSyntaxErrReply()
 	}
 	key := string(args[0])
 	size := (len(args) - 1) / 2
@@ -79,12 +79,9 @@ func ZAdd(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(i))
 }
 
-// ZScore gets score of a member in sortedset
-func ZScore(db *DB, args [][]byte) redis.Reply {
+// execZScore gets score of a member in sortedset
+func execZScore(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zscore' command")
-	}
 	key := string(args[0])
 	member := string(args[1])
 
@@ -106,12 +103,9 @@ func ZScore(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply([]byte(value))
 }
 
-// ZRank gets index of a member in sortedset, ascending order, start from 0
-func ZRank(db *DB, args [][]byte) redis.Reply {
+// execZRank gets index of a member in sortedset, ascending order, start from 0
+func execZRank(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zrank' command")
-	}
 	key := string(args[0])
 	member := string(args[1])
 
@@ -133,12 +127,9 @@ func ZRank(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(rank)
 }
 
-// ZRevRank gets index of a member in sortedset, descending order, start from 0
-func ZRevRank(db *DB, args [][]byte) redis.Reply {
+// execZRevRank gets index of a member in sortedset, descending order, start from 0
+func execZRevRank(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zrevrank' command")
-	}
 	key := string(args[0])
 	member := string(args[1])
 
@@ -160,12 +151,9 @@ func ZRevRank(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(rank)
 }
 
-// ZCard gets number of members in sortedset
-func ZCard(db *DB, args [][]byte) redis.Reply {
+// execZCard gets number of members in sortedset
+func execZCard(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zcard' command")
-	}
 	key := string(args[0])
 
 	// get entity
@@ -182,8 +170,8 @@ func ZCard(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(sortedSet.Len())
 }
 
-// ZRange gets members in range, sort by score in ascending order
-func ZRange(db *DB, args [][]byte) redis.Reply {
+// execZRange gets members in range, sort by score in ascending order
+func execZRange(db *DB, args [][]byte) redis.Reply {
 	// parse args
 	if len(args) != 3 && len(args) != 4 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'zrange' command")
@@ -207,8 +195,8 @@ func ZRange(db *DB, args [][]byte) redis.Reply {
 	return range0(db, key, start, stop, withScores, false)
 }
 
-// ZRevRange gets members in range, sort by score in descending order
-func ZRevRange(db *DB, args [][]byte) redis.Reply {
+// execZRevRange gets members in range, sort by score in descending order
+func execZRevRange(db *DB, args [][]byte) redis.Reply {
 	// parse args
 	if len(args) != 3 && len(args) != 4 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'zrevrange' command")
@@ -291,11 +279,8 @@ func range0(db *DB, key string, start int64, stop int64, withScores bool, desc b
 	return reply.MakeMultiBulkReply(result)
 }
 
-// ZCount gets number of members which score within given range
-func ZCount(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zcount' command")
-	}
+// execZCount gets number of members which score within given range
+func execZCount(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	min, err := SortedSet.ParseScoreBorder(string(args[1]))
@@ -362,8 +347,8 @@ func rangeByScore0(db *DB, key string, min *SortedSet.ScoreBorder, max *SortedSe
 	return reply.MakeMultiBulkReply(result)
 }
 
-// ZRangeByScore gets members which score within given range, in ascending order
-func ZRangeByScore(db *DB, args [][]byte) redis.Reply {
+// execZRangeByScore gets members which score within given range, in ascending order
+func execZRangeByScore(db *DB, args [][]byte) redis.Reply {
 	if len(args) < 3 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'zrangebyscore' command")
 	}
@@ -409,8 +394,8 @@ func ZRangeByScore(db *DB, args [][]byte) redis.Reply {
 	return rangeByScore0(db, key, min, max, offset, limit, withScores, false)
 }
 
-// ZRevRangeByScore gets number of members which score within given range, in descending order
-func ZRevRangeByScore(db *DB, args [][]byte) redis.Reply {
+// execZRevRangeByScore gets number of members which score within given range, in descending order
+func execZRevRangeByScore(db *DB, args [][]byte) redis.Reply {
 	if len(args) < 3 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'zrangebyscore' command")
 	}
@@ -456,8 +441,8 @@ func ZRevRangeByScore(db *DB, args [][]byte) redis.Reply {
 	return rangeByScore0(db, key, min, max, offset, limit, withScores, true)
 }
 
-// ZRemRangeByScore removes members which score within given range
-func ZRemRangeByScore(db *DB, args [][]byte) redis.Reply {
+// execZRemRangeByScore removes members which score within given range
+func execZRemRangeByScore(db *DB, args [][]byte) redis.Reply {
 	if len(args) != 3 {
 		return reply.MakeErrReply("ERR wrong number of arguments for 'zremrangebyscore' command")
 	}
@@ -492,11 +477,8 @@ func ZRemRangeByScore(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(removed)
 }
 
-// ZRemRangeByRank removes members within given indexes
-func ZRemRangeByRank(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zremrangebyrank' command")
-	}
+// execZRemRangeByRank removes members within given indexes
+func execZRemRangeByRank(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	start, err := strconv.ParseInt(string(args[1]), 10, 64)
 	if err != nil {
@@ -549,12 +531,9 @@ func ZRemRangeByRank(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(removed)
 }
 
-// ZRem removes given members
-func ZRem(db *DB, args [][]byte) redis.Reply {
+// execZRem removes given members
+func execZRem(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zrem' command")
-	}
 	key := string(args[0])
 	fields := make([]string, len(args)-1)
 	fieldArgs := args[1:]
@@ -586,11 +565,8 @@ func ZRem(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(deleted)
 }
 
-// ZIncrBy increments the score of a member
-func ZIncrBy(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'zincrby' command")
-	}
+// execZIncrBy increments the score of a member
+func execZIncrBy(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	rawDelta := string(args[1])
 	field := string(args[2])
@@ -620,3 +596,20 @@ func ZIncrBy(db *DB, args [][]byte) redis.Reply {
 	db.AddAof(makeAofCmd("zincrby", args))
 	return reply.MakeBulkReply(bytes)
 }
+
+func init() {
+	RegisterCommand("ZAdd", execZAdd, nil, -4)
+	RegisterCommand("ZScore", execZScore, nil, 3)
+	RegisterCommand("ZIncrBy", execZIncrBy, nil, 4)
+	RegisterCommand("ZRank", execZRank, nil, 3)
+	RegisterCommand("ZCount", execZCount, nil, 4)
+	RegisterCommand("ZRevRank", execZRevRank, nil, 3)
+	RegisterCommand("ZCard", execZCard, nil, 2)
+	RegisterCommand("ZRange", execZRange, nil, -4)
+	RegisterCommand("ZRangeByScore", execZRangeByScore, nil, -4)
+	RegisterCommand("ZRange", execZRevRange, nil, -4)
+	RegisterCommand("ZRangeByScore", execZRevRangeByScore, nil, -4)
+	RegisterCommand("ZRem", execZRem, nil, -3)
+	RegisterCommand("ZRemRangeByScore", execZRemRangeByScore, nil, 4)
+	RegisterCommand("ZRemRangeByRank", execZRemRangeByRank, nil, 4)
+}
diff --git a/sortedset_test.go b/sortedset_test.go
index 8911ee9..3475648 100644
--- a/sortedset_test.go
+++ b/sortedset_test.go
@@ -9,7 +9,7 @@ import (
 )
 
 func TestZAdd(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 
 	// add new members
@@ -22,18 +22,18 @@ func TestZAdd(t *testing.T) {
 		scores[i] = rand.Float64()
 		setArgs = append(setArgs, strconv.FormatFloat(scores[i], 'f', -1, 64), members[i])
 	}
-	result := ZAdd(testDB, utils.ToBytesList(setArgs...))
+	result := execZAdd(testDB, utils.ToBytesList(setArgs...))
 	asserts.AssertIntReply(t, result, size)
 
 	// test zscore and zrank
 	for i, member := range members {
-		result := ZScore(testDB, utils.ToBytesList(key, member))
+		result := execZScore(testDB, utils.ToBytesList(key, member))
 		score := strconv.FormatFloat(scores[i], 'f', -1, 64)
 		asserts.AssertBulkReply(t, result, score)
 	}
 
 	// test zcard
-	result = ZCard(testDB, utils.ToBytesList(key))
+	result = execZCard(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, size)
 
 	// update members
@@ -42,19 +42,19 @@ func TestZAdd(t *testing.T) {
 		scores[i] = rand.Float64() + 100
 		setArgs = append(setArgs, strconv.FormatFloat(scores[i], 'f', -1, 64), members[i])
 	}
-	result = ZAdd(testDB, utils.ToBytesList(setArgs...))
+	result = execZAdd(testDB, utils.ToBytesList(setArgs...))
 	asserts.AssertIntReply(t, result, 0) // return number of new members
 
 	// test updated score
 	for i, member := range members {
-		result := ZScore(testDB, utils.ToBytesList(key, member))
+		result := execZScore(testDB, utils.ToBytesList(key, member))
 		score := strconv.FormatFloat(scores[i], 'f', -1, 64)
 		asserts.AssertBulkReply(t, result, score)
 	}
 }
 
 func TestZRank(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils.RandString(10)
 	members := make([]string, size)
@@ -65,21 +65,21 @@ func TestZRank(t *testing.T) {
 		scores[i] = i
 		setArgs = append(setArgs, strconv.FormatInt(int64(scores[i]), 10), members[i])
 	}
-	ZAdd(testDB, utils.ToBytesList(setArgs...))
+	execZAdd(testDB, utils.ToBytesList(setArgs...))
 
 	// test  zrank
 	for i, member := range members {
-		result := ZRank(testDB, utils.ToBytesList(key, member))
+		result := execZRank(testDB, utils.ToBytesList(key, member))
 		asserts.AssertIntReply(t, result, i)
 
-		result = ZRevRank(testDB, utils.ToBytesList(key, member))
+		result = execZRevRank(testDB, utils.ToBytesList(key, member))
 		asserts.AssertIntReply(t, result, size-i-1)
 	}
 }
 
 func TestZRange(t *testing.T) {
 	// prepare
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils.RandString(10)
 	members := make([]string, size)
@@ -90,7 +90,7 @@ func TestZRange(t *testing.T) {
 		scores[i] = i
 		setArgs = append(setArgs, strconv.FormatInt(int64(scores[i]), 10), members[i])
 	}
-	ZAdd(testDB, utils.ToBytesList(setArgs...))
+	execZAdd(testDB, utils.ToBytesList(setArgs...))
 	reverseMembers := make([]string, size)
 	for i, v := range members {
 		reverseMembers[size-i-1] = v
@@ -98,39 +98,39 @@ func TestZRange(t *testing.T) {
 
 	start := "0"
 	end := "9"
-	result := ZRange(testDB, utils.ToBytesList(key, start, end))
+	result := execZRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, members[0:10])
-	result = ZRange(testDB, utils.ToBytesList(key, start, end, "WITHSCORES"))
+	result = execZRange(testDB, utils.ToBytesList(key, start, end, "WITHSCORES"))
 	asserts.AssertMultiBulkReplySize(t, result, 20)
-	result = ZRevRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRevRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, reverseMembers[0:10])
 
 	start = "0"
 	end = "200"
-	result = ZRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, members)
-	result = ZRevRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRevRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, reverseMembers)
 
 	start = "0"
 	end = "-10"
-	result = ZRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, members[0:size-10+1])
-	result = ZRevRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRevRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, reverseMembers[0:size-10+1])
 
 	start = "0"
 	end = "-200"
-	result = ZRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, members[0:0])
-	result = ZRevRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRevRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, reverseMembers[0:0])
 
 	start = "-10"
 	end = "-1"
-	result = ZRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, members[90:])
-	result = ZRevRange(testDB, utils.ToBytesList(key, start, end))
+	result = execZRevRange(testDB, utils.ToBytesList(key, start, end))
 	asserts.AssertMultiBulkReply(t, result, reverseMembers[90:])
 }
 
@@ -144,7 +144,7 @@ func reverse(src []string) []string {
 
 func TestZRangeByScore(t *testing.T) {
 	// prepare
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils.RandString(10)
 	members := make([]string, size)
@@ -155,49 +155,49 @@ func TestZRangeByScore(t *testing.T) {
 		scores[i] = i
 		setArgs = append(setArgs, strconv.FormatInt(int64(scores[i]), 10), members[i])
 	}
-	result := ZAdd(testDB, utils.ToBytesList(setArgs...))
+	result := execZAdd(testDB, utils.ToBytesList(setArgs...))
 	asserts.AssertIntReply(t, result, size)
 
 	min := "20"
 	max := "30"
-	result = ZRangeByScore(testDB, utils.ToBytesList(key, min, max))
+	result = execZRangeByScore(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertMultiBulkReply(t, result, members[20:31])
-	result = ZRangeByScore(testDB, utils.ToBytesList(key, min, max, "WITHSCORES"))
+	result = execZRangeByScore(testDB, utils.ToBytesList(key, min, max, "WITHSCORES"))
 	asserts.AssertMultiBulkReplySize(t, result, 22)
-	result = ZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
+	result = execZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
 	asserts.AssertMultiBulkReply(t, result, reverse(members[20:31]))
 
 	min = "-10"
 	max = "10"
-	result = ZRangeByScore(testDB, utils.ToBytesList(key, min, max))
+	result = execZRangeByScore(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertMultiBulkReply(t, result, members[0:11])
-	result = ZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
+	result = execZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
 	asserts.AssertMultiBulkReply(t, result, reverse(members[0:11]))
 
 	min = "90"
 	max = "110"
-	result = ZRangeByScore(testDB, utils.ToBytesList(key, min, max))
+	result = execZRangeByScore(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertMultiBulkReply(t, result, members[90:])
-	result = ZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
+	result = execZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
 	asserts.AssertMultiBulkReply(t, result, reverse(members[90:]))
 
 	min = "(20"
 	max = "(30"
-	result = ZRangeByScore(testDB, utils.ToBytesList(key, min, max))
+	result = execZRangeByScore(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertMultiBulkReply(t, result, members[21:30])
-	result = ZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
+	result = execZRevRangeByScore(testDB, utils.ToBytesList(key, max, min))
 	asserts.AssertMultiBulkReply(t, result, reverse(members[21:30]))
 
 	min = "20"
 	max = "40"
-	result = ZRangeByScore(testDB, utils.ToBytesList(key, min, max, "LIMIT", "5", "5"))
+	result = execZRangeByScore(testDB, utils.ToBytesList(key, min, max, "LIMIT", "5", "5"))
 	asserts.AssertMultiBulkReply(t, result, members[25:30])
-	result = ZRevRangeByScore(testDB, utils.ToBytesList(key, max, min, "LIMIT", "5", "5"))
+	result = execZRevRangeByScore(testDB, utils.ToBytesList(key, max, min, "LIMIT", "5", "5"))
 	asserts.AssertMultiBulkReply(t, result, reverse(members[31:36]))
 }
 
 func TestZRem(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils.RandString(10)
 	members := make([]string, size)
@@ -208,17 +208,17 @@ func TestZRem(t *testing.T) {
 		scores[i] = i
 		setArgs = append(setArgs, strconv.FormatInt(int64(scores[i]), 10), members[i])
 	}
-	ZAdd(testDB, utils.ToBytesList(setArgs...))
+	execZAdd(testDB, utils.ToBytesList(setArgs...))
 
 	args := []string{key}
 	args = append(args, members[0:10]...)
-	result := ZRem(testDB, utils.ToBytesList(args...))
+	result := execZRem(testDB, utils.ToBytesList(args...))
 	asserts.AssertIntReply(t, result, 10)
-	result = ZCard(testDB, utils.ToBytesList(key))
+	result = execZCard(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, size-10)
 
 	// test ZRemRangeByRank
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size = 100
 	key = utils.RandString(10)
 	members = make([]string, size)
@@ -229,15 +229,15 @@ func TestZRem(t *testing.T) {
 		scores[i] = i
 		setArgs = append(setArgs, strconv.FormatInt(int64(scores[i]), 10), members[i])
 	}
-	ZAdd(testDB, utils.ToBytesList(setArgs...))
+	execZAdd(testDB, utils.ToBytesList(setArgs...))
 
-	result = ZRemRangeByRank(testDB, utils.ToBytesList(key, "0", "9"))
+	result = execZRemRangeByRank(testDB, utils.ToBytesList(key, "0", "9"))
 	asserts.AssertIntReply(t, result, 10)
-	result = ZCard(testDB, utils.ToBytesList(key))
+	result = execZCard(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, size-10)
 
 	// test ZRemRangeByScore
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size = 100
 	key = utils.RandString(10)
 	members = make([]string, size)
@@ -248,17 +248,17 @@ func TestZRem(t *testing.T) {
 		scores[i] = i
 		setArgs = append(setArgs, strconv.FormatInt(int64(scores[i]), 10), members[i])
 	}
-	ZAdd(testDB, utils.ToBytesList(setArgs...))
+	execZAdd(testDB, utils.ToBytesList(setArgs...))
 
-	result = ZRemRangeByScore(testDB, utils.ToBytesList(key, "0", "9"))
+	result = execZRemRangeByScore(testDB, utils.ToBytesList(key, "0", "9"))
 	asserts.AssertIntReply(t, result, 10)
-	result = ZCard(testDB, utils.ToBytesList(key))
+	result = execZCard(testDB, utils.ToBytesList(key))
 	asserts.AssertIntReply(t, result, size-10)
 }
 
 func TestZCount(t *testing.T) {
 	// prepare
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 100
 	key := utils.RandString(10)
 	members := make([]string, size)
@@ -269,37 +269,37 @@ func TestZCount(t *testing.T) {
 		scores[i] = i
 		setArgs = append(setArgs, strconv.FormatInt(int64(scores[i]), 10), members[i])
 	}
-	ZAdd(testDB, utils.ToBytesList(setArgs...))
+	execZAdd(testDB, utils.ToBytesList(setArgs...))
 
 	min := "20"
 	max := "30"
-	result := ZCount(testDB, utils.ToBytesList(key, min, max))
+	result := execZCount(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertIntReply(t, result, 11)
 
 	min = "-10"
 	max = "10"
-	result = ZCount(testDB, utils.ToBytesList(key, min, max))
+	result = execZCount(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertIntReply(t, result, 11)
 
 	min = "90"
 	max = "110"
-	result = ZCount(testDB, utils.ToBytesList(key, min, max))
+	result = execZCount(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertIntReply(t, result, 10)
 
 	min = "(20"
 	max = "(30"
-	result = ZCount(testDB, utils.ToBytesList(key, min, max))
+	result = execZCount(testDB, utils.ToBytesList(key, min, max))
 	asserts.AssertIntReply(t, result, 9)
 }
 
 func TestZIncrBy(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils.RandString(10)
-	result := ZIncrBy(testDB, utils.ToBytesList(key, "10", "a"))
+	result := execZIncrBy(testDB, utils.ToBytesList(key, "10", "a"))
 	asserts.AssertBulkReply(t, result, "10")
-	result = ZIncrBy(testDB, utils.ToBytesList(key, "10", "a"))
+	result = execZIncrBy(testDB, utils.ToBytesList(key, "10", "a"))
 	asserts.AssertBulkReply(t, result, "20")
 
-	result = ZScore(testDB, utils.ToBytesList(key, "a"))
+	result = execZScore(testDB, utils.ToBytesList(key, "a"))
 	asserts.AssertBulkReply(t, result, "20")
 }
diff --git a/string.go b/string.go
index f3c97b8..a44ee61 100644
--- a/string.go
+++ b/string.go
@@ -21,11 +21,8 @@ func (db *DB) getAsString(key string) ([]byte, reply.ErrorReply) {
 	return bytes, nil
 }
 
-// Get returns string value bound to the given key
-func Get(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'get' command")
-	}
+// execGet returns string value bound to the given key
+func execGet(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	bytes, err := db.getAsString(key)
 	if err != nil {
@@ -45,11 +42,8 @@ const (
 
 const unlimitedTTL int64 = 0
 
-// Set sets string value and time to live to the given key
-func Set(db *DB, args [][]byte) redis.Reply {
-	if len(args) < 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'set' command")
-	}
+// execSet sets string value and time to live to the given key
+func execSet(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	value := args[1]
 	policy := upsertPolicy
@@ -149,11 +143,8 @@ func Set(db *DB, args [][]byte) redis.Reply {
 	return &reply.NullBulkReply{}
 }
 
-// SetNX sets string if not exists
-func SetNX(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'setnx' command")
-	}
+// execSetNX sets string if not exists
+func execSetNX(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	value := args[1]
 	entity := &DataEntity{
@@ -164,11 +155,8 @@ func SetNX(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(int64(result))
 }
 
-// SetEX sets string and its ttl
-func SetEX(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'setex' command")
-	}
+// execSetEX sets string and its ttl
+func execSetEX(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	value := args[2]
 
@@ -196,11 +184,8 @@ func SetEX(db *DB, args [][]byte) redis.Reply {
 	return &reply.OkReply{}
 }
 
-// PSetEX set a key's time to live in  milliseconds
-func PSetEX(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 3 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'setex' command")
-	}
+// execPSetEX set a key's time to live in  milliseconds
+func execPSetEX(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	value := args[2]
 
@@ -228,10 +213,10 @@ func PSetEX(db *DB, args [][]byte) redis.Reply {
 	return &reply.OkReply{}
 }
 
-// MSet sets multi key-value in database
-func MSet(db *DB, args [][]byte) redis.Reply {
-	if len(args)%2 != 0 || len(args) == 0 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'mset' command")
+// execMSet sets multi key-value in database
+func execMSet(db *DB, args [][]byte) redis.Reply {
+	if len(args)%2 != 0 {
+		return reply.MakeSyntaxErrReply()
 	}
 
 	size := len(args) / 2
@@ -253,11 +238,8 @@ func MSet(db *DB, args [][]byte) redis.Reply {
 	return &reply.OkReply{}
 }
 
-// MGet get multi key-value from database
-func MGet(db *DB, args [][]byte) redis.Reply {
-	if len(args) == 0 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'mget' command")
-	}
+// execMGet get multi key-value from database
+func execMGet(db *DB, args [][]byte) redis.Reply {
 	keys := make([]string, len(args))
 	for i, v := range args {
 		keys[i] = string(v)
@@ -281,11 +263,11 @@ func MGet(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeMultiBulkReply(result)
 }
 
-// MSetNX sets multi key-value in database, only if none of the given keys exist
-func MSetNX(db *DB, args [][]byte) redis.Reply {
+// execMSetNX sets multi key-value in database, only if none of the given keys exist
+func execMSetNX(db *DB, args [][]byte) redis.Reply {
 	// parse args
-	if len(args)%2 != 0 || len(args) == 0 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'msetnx' command")
+	if len(args)%2 != 0 {
+		return reply.MakeSyntaxErrReply()
 	}
 	size := len(args) / 2
 	values := make([][]byte, size)
@@ -314,11 +296,8 @@ func MSetNX(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(1)
 }
 
-// GetSet sets value of a string-type key and returns its old value
-func GetSet(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'getset' command")
-	}
+// execGetSet sets value of a string-type key and returns its old value
+func execGetSet(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	value := args[1]
 
@@ -336,11 +315,8 @@ func GetSet(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(old)
 }
 
-// Incr increments the integer value of a key by one
-func Incr(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'incr' command")
-	}
+// execIncr increments the integer value of a key by one
+func execIncr(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	db.Lock(key)
@@ -368,11 +344,8 @@ func Incr(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(1)
 }
 
-// IncrBy increments the integer value of a key by given value
-func IncrBy(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'incrby' command")
-	}
+// execIncrBy increments the integer value of a key by given value
+func execIncrBy(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	rawDelta := string(args[1])
 	delta, err := strconv.ParseInt(rawDelta, 10, 64)
@@ -406,11 +379,8 @@ func IncrBy(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(delta)
 }
 
-// IncrByFloat increments the float value of a key by given value
-func IncrByFloat(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'incrbyfloat' command")
-	}
+// execIncrByFloat increments the float value of a key by given value
+func execIncrByFloat(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	rawDelta := string(args[1])
 	delta, err := decimal.NewFromString(rawDelta)
@@ -444,11 +414,8 @@ func IncrByFloat(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeBulkReply(args[1])
 }
 
-// Decr decrements the integer value of a key by one
-func Decr(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 1 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'decr' command")
-	}
+// execDecr decrements the integer value of a key by one
+func execDecr(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 
 	db.Lock(key)
@@ -477,11 +444,8 @@ func Decr(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(-1)
 }
 
-// DecrBy decrements the integer value of a key by onedecrement
-func DecrBy(db *DB, args [][]byte) redis.Reply {
-	if len(args) != 2 {
-		return reply.MakeErrReply("ERR wrong number of arguments for 'decrby' command")
-	}
+// execDecrBy decrements the integer value of a key by onedecrement
+func execDecrBy(db *DB, args [][]byte) redis.Reply {
 	key := string(args[0])
 	rawDelta := string(args[1])
 	delta, err := strconv.ParseInt(rawDelta, 10, 64)
@@ -514,3 +478,22 @@ func DecrBy(db *DB, args [][]byte) redis.Reply {
 	db.AddAof(makeAofCmd("decrby", args))
 	return reply.MakeIntReply(-delta)
 }
+
+func init() {
+	RegisterCommand("Set", execSet, nil, -3)
+	RegisterCommand("SetNx", execSetNX, nil, 3)
+	RegisterCommand("SetEX", execSetEX, nil, 4)
+	RegisterCommand("PSetEX", execPSetEX, nil, 4)
+	RegisterCommand("MSet", execMSet, nil, -3)
+	RegisterCommand("MGet", execMGet, nil, -2)
+	RegisterCommand("MSetNX", execMSetNX, nil, -3)
+	RegisterCommand("Get", execGet, nil, 2)
+	RegisterCommand("MSet", execMSet, nil, -3)
+	RegisterCommand("GetSet", execGetSet, nil, 3)
+	RegisterCommand("MSet", execMSet, nil, -3)
+	RegisterCommand("Incr", execIncr, nil, 2)
+	RegisterCommand("IncrBy", execIncrBy, nil, 3)
+	RegisterCommand("IncrByFloat", execIncrByFloat, nil, 3)
+	RegisterCommand("Decr", execDecr, nil, 2)
+	RegisterCommand("DecrBy", execDecrBy, nil, 3)
+}
diff --git a/string_test.go b/string_test.go
index fa28afd..c646036 100644
--- a/string_test.go
+++ b/string_test.go
@@ -13,55 +13,55 @@ import (
 var testDB = makeTestDB()
 
 func TestSet(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	value := utils2.RandString(10)
 
 	// normal set
-	Set(testDB, utils2.ToBytesList(key, value))
-	actual := Get(testDB, utils2.ToBytesList(key))
+	execSet(testDB, utils2.ToBytesList(key, value))
+	actual := execGet(testDB, utils2.ToBytesList(key))
 	expected := reply.MakeBulkReply([]byte(value))
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("expected: " + string(expected.ToBytes()) + ", actual: " + string(actual.ToBytes()))
 	}
 
 	// set nx
-	actual = Set(testDB, utils2.ToBytesList(key, value, "NX"))
+	actual = execSet(testDB, utils2.ToBytesList(key, value, "NX"))
 	if _, ok := actual.(*reply.NullBulkReply); !ok {
 		t.Error("expected true actual false")
 	}
 
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key = utils2.RandString(10)
 	value = utils2.RandString(10)
-	Set(testDB, utils2.ToBytesList(key, value, "NX"))
-	actual = Get(testDB, utils2.ToBytesList(key))
+	execSet(testDB, utils2.ToBytesList(key, value, "NX"))
+	actual = execGet(testDB, utils2.ToBytesList(key))
 	expected = reply.MakeBulkReply([]byte(value))
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("expected: " + string(expected.ToBytes()) + ", actual: " + string(actual.ToBytes()))
 	}
 
 	// set xx
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key = utils2.RandString(10)
 	value = utils2.RandString(10)
-	actual = Set(testDB, utils2.ToBytesList(key, value, "XX"))
+	actual = execSet(testDB, utils2.ToBytesList(key, value, "XX"))
 	if _, ok := actual.(*reply.NullBulkReply); !ok {
 		t.Error("expected true actually false ")
 	}
 
-	Set(testDB, utils2.ToBytesList(key, value))
-	Set(testDB, utils2.ToBytesList(key, value, "XX"))
-	actual = Get(testDB, utils2.ToBytesList(key))
+	execSet(testDB, utils2.ToBytesList(key, value))
+	execSet(testDB, utils2.ToBytesList(key, value, "XX"))
+	actual = execGet(testDB, utils2.ToBytesList(key))
 	asserts.AssertBulkReply(t, actual, value)
 
 	// set ex
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 	ttl := "1000"
-	Set(testDB, utils2.ToBytesList(key, value, "EX", ttl))
-	actual = Get(testDB, utils2.ToBytesList(key))
+	execSet(testDB, utils2.ToBytesList(key, value, "EX", ttl))
+	actual = execGet(testDB, utils2.ToBytesList(key))
 	asserts.AssertBulkReply(t, actual, value)
-	actual = TTL(testDB, utils2.ToBytesList(key))
+	actual = execTTL(testDB, utils2.ToBytesList(key))
 	intResult, ok := actual.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", actual.ToBytes()))
@@ -73,12 +73,12 @@ func TestSet(t *testing.T) {
 	}
 
 	// set px
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 	ttlPx := "1000000"
-	Set(testDB, utils2.ToBytesList(key, value, "PX", ttlPx))
-	actual = Get(testDB, utils2.ToBytesList(key))
+	execSet(testDB, utils2.ToBytesList(key, value, "PX", ttlPx))
+	actual = execGet(testDB, utils2.ToBytesList(key))
 	asserts.AssertBulkReply(t, actual, value)
-	actual = TTL(testDB, utils2.ToBytesList(key))
+	actual = execTTL(testDB, utils2.ToBytesList(key))
 	intResult, ok = actual.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", actual.ToBytes()))
@@ -91,17 +91,17 @@ func TestSet(t *testing.T) {
 }
 
 func TestSetNX(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	value := utils2.RandString(10)
-	SetNX(testDB, utils2.ToBytesList(key, value))
-	actual := Get(testDB, utils2.ToBytesList(key))
+	execSetNX(testDB, utils2.ToBytesList(key, value))
+	actual := execGet(testDB, utils2.ToBytesList(key))
 	expected := reply.MakeBulkReply([]byte(value))
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("expected: " + string(expected.ToBytes()) + ", actual: " + string(actual.ToBytes()))
 	}
 
-	actual = SetNX(testDB, utils2.ToBytesList(key, value))
+	actual = execSetNX(testDB, utils2.ToBytesList(key, value))
 	expected2 := reply.MakeIntReply(int64(0))
 	if !utils.BytesEquals(actual.ToBytes(), expected2.ToBytes()) {
 		t.Error("expected: " + string(expected2.ToBytes()) + ", actual: " + string(actual.ToBytes()))
@@ -109,15 +109,15 @@ func TestSetNX(t *testing.T) {
 }
 
 func TestSetEX(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	value := utils2.RandString(10)
 	ttl := "1000"
 
-	SetEX(testDB, utils2.ToBytesList(key, ttl, value))
-	actual := Get(testDB, utils2.ToBytesList(key))
+	execSetEX(testDB, utils2.ToBytesList(key, ttl, value))
+	actual := execGet(testDB, utils2.ToBytesList(key))
 	asserts.AssertBulkReply(t, actual, value)
-	actual = TTL(testDB, utils2.ToBytesList(key))
+	actual = execTTL(testDB, utils2.ToBytesList(key))
 	intResult, ok := actual.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", actual.ToBytes()))
@@ -130,15 +130,15 @@ func TestSetEX(t *testing.T) {
 }
 
 func TestPSetEX(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	value := utils2.RandString(10)
 	ttl := "1000000"
 
-	PSetEX(testDB, utils2.ToBytesList(key, ttl, value))
-	actual := Get(testDB, utils2.ToBytesList(key))
+	execPSetEX(testDB, utils2.ToBytesList(key, ttl, value))
+	actual := execGet(testDB, utils2.ToBytesList(key))
 	asserts.AssertBulkReply(t, actual, value)
-	actual = PTTL(testDB, utils2.ToBytesList(key))
+	actual = execPTTL(testDB, utils2.ToBytesList(key))
 	intResult, ok := actual.(*reply.IntReply)
 	if !ok {
 		t.Error(fmt.Sprintf("expected int reply, actually %s", actual.ToBytes()))
@@ -151,7 +151,7 @@ func TestPSetEX(t *testing.T) {
 }
 
 func TestMSet(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 10
 	keys := make([]string, size)
 	values := make([][]byte, size)
@@ -162,8 +162,8 @@ func TestMSet(t *testing.T) {
 		values[i] = []byte(value)
 		args = append(args, keys[i], value)
 	}
-	MSet(testDB, utils2.ToBytesList(args...))
-	actual := MGet(testDB, utils2.ToBytesList(keys...))
+	execMSet(testDB, utils2.ToBytesList(args...))
+	actual := execMGet(testDB, utils2.ToBytesList(keys...))
 	expected := reply.MakeMultiBulkReply(values)
 	if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 		t.Error("expected: " + string(expected.ToBytes()) + ", actual: " + string(actual.ToBytes()))
@@ -171,40 +171,40 @@ func TestMSet(t *testing.T) {
 }
 
 func TestIncr(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 10
 	key := utils2.RandString(10)
 	for i := 0; i < size; i++ {
-		Incr(testDB, utils2.ToBytesList(key))
-		actual := Get(testDB, utils2.ToBytesList(key))
+		execIncr(testDB, utils2.ToBytesList(key))
+		actual := execGet(testDB, utils2.ToBytesList(key))
 		expected := reply.MakeBulkReply([]byte(strconv.FormatInt(int64(i+1), 10)))
 		if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 			t.Error("expected: " + string(expected.ToBytes()) + ", actual: " + string(actual.ToBytes()))
 		}
 	}
 	for i := 0; i < size; i++ {
-		IncrBy(testDB, utils2.ToBytesList(key, "-1"))
-		actual := Get(testDB, utils2.ToBytesList(key))
+		execIncrBy(testDB, utils2.ToBytesList(key, "-1"))
+		actual := execGet(testDB, utils2.ToBytesList(key))
 		expected := reply.MakeBulkReply([]byte(strconv.FormatInt(int64(size-i-1), 10)))
 		if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 			t.Error("expected: " + string(expected.ToBytes()) + ", actual: " + string(actual.ToBytes()))
 		}
 	}
 
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key = utils2.RandString(10)
 	for i := 0; i < size; i++ {
-		IncrBy(testDB, utils2.ToBytesList(key, "1"))
-		actual := Get(testDB, utils2.ToBytesList(key))
+		execIncrBy(testDB, utils2.ToBytesList(key, "1"))
+		actual := execGet(testDB, utils2.ToBytesList(key))
 		expected := reply.MakeBulkReply([]byte(strconv.FormatInt(int64(i+1), 10)))
 		if !utils.BytesEquals(actual.ToBytes(), expected.ToBytes()) {
 			t.Error("expected: " + string(expected.ToBytes()) + ", actual: " + string(actual.ToBytes()))
 		}
 	}
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 	for i := 0; i < size; i++ {
-		IncrByFloat(testDB, utils2.ToBytesList(key, "-1.0"))
-		actual := Get(testDB, utils2.ToBytesList(key))
+		execIncrByFloat(testDB, utils2.ToBytesList(key, "-1.0"))
+		actual := execGet(testDB, utils2.ToBytesList(key))
 		expected := -i - 1
 		bulk, ok := actual.(*reply.BulkReply)
 		if !ok {
@@ -224,18 +224,18 @@ func TestIncr(t *testing.T) {
 }
 
 func TestDecr(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 10
 	key := utils2.RandString(10)
 	for i := 0; i < size; i++ {
-		Decr(testDB, utils2.ToBytesList(key))
-		actual := Get(testDB, utils2.ToBytesList(key))
+		execDecr(testDB, utils2.ToBytesList(key))
+		actual := execGet(testDB, utils2.ToBytesList(key))
 		asserts.AssertBulkReply(t, actual, strconv.Itoa(-i-1))
 	}
-	Del(testDB, utils2.ToBytesList(key))
+	testDB.Remove(key)
 	for i := 0; i < size; i++ {
-		DecrBy(testDB, utils2.ToBytesList(key, "1"))
-		actual := Get(testDB, utils2.ToBytesList(key))
+		execDecrBy(testDB, utils2.ToBytesList(key, "1"))
+		actual := execGet(testDB, utils2.ToBytesList(key))
 		expected := -i - 1
 		bulk, ok := actual.(*reply.BulkReply)
 		if !ok {
@@ -255,11 +255,11 @@ func TestDecr(t *testing.T) {
 }
 
 func TestGetSet(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	key := utils2.RandString(10)
 	value := utils2.RandString(10)
 
-	result := GetSet(testDB, utils2.ToBytesList(key, value))
+	result := execGetSet(testDB, utils2.ToBytesList(key, value))
 	_, ok := result.(*reply.NullBulkReply)
 	if !ok {
 		t.Errorf("expect null bulk reply, get: %s", string(result.ToBytes()))
@@ -267,23 +267,23 @@ func TestGetSet(t *testing.T) {
 	}
 
 	value2 := utils2.RandString(10)
-	result = GetSet(testDB, utils2.ToBytesList(key, value2))
+	result = execGetSet(testDB, utils2.ToBytesList(key, value2))
 	asserts.AssertBulkReply(t, result, value)
-	result = Get(testDB, utils2.ToBytesList(key))
+	result = execGet(testDB, utils2.ToBytesList(key))
 	asserts.AssertBulkReply(t, result, value2)
 }
 
 func TestMSetNX(t *testing.T) {
-	FlushAll(testDB, [][]byte{})
+	execFlushAll(testDB, [][]byte{})
 	size := 10
 	args := make([]string, 0, size*2)
 	for i := 0; i < size; i++ {
 		str := utils2.RandString(10)
 		args = append(args, str, str)
 	}
-	result := MSetNX(testDB, utils2.ToBytesList(args...))
+	result := execMSetNX(testDB, utils2.ToBytesList(args...))
 	asserts.AssertIntReply(t, result, 1)
 
-	result = MSetNX(testDB, utils2.ToBytesList(args[0:4]...))
+	result = execMSetNX(testDB, utils2.ToBytesList(args[0:4]...))
 	asserts.AssertIntReply(t, result, 0)
 }