diff --git a/string.go b/string.go
index 769c434..87a0137 100644
--- a/string.go
+++ b/string.go
@@ -473,6 +473,34 @@ func execDecrBy(db *DB, args [][]byte) redis.Reply {
 	return reply.MakeIntReply(-delta)
 }
 
+// execStrLen returns len of string value bound to the given key
+func execStrLen(db *DB, args [][]byte) redis.Reply {
+	key := string(args[0])
+	bytes, err := db.getAsString(key)
+	if err != nil {
+		return err
+	}
+	if bytes == nil {
+		return reply.MakeIntReply(0)
+	}
+	return reply.MakeIntReply(int64(len(bytes)))
+}
+
+// execAppend sets string value and time to live to the given key
+func execAppend(db *DB, args [][]byte) redis.Reply {
+	key := string(args[0])
+	bytes, err := db.getAsString(key)
+	if err != nil {
+		return err
+	}
+	bytes = append(bytes, args[1]...)
+	db.PutEntity(key, &DataEntity{
+		Data: bytes,
+	})
+	db.AddAof(makeAofCmd("append", args))
+	return reply.MakeIntReply(int64(len(bytes)))
+}
+
 func init() {
 	RegisterCommand("Set", execSet, writeFirstKey, rollbackFirstKey, -3)
 	RegisterCommand("SetNx", execSetNX, writeFirstKey, rollbackFirstKey, 3)
@@ -488,4 +516,6 @@ func init() {
 	RegisterCommand("IncrByFloat", execIncrByFloat, writeFirstKey, rollbackFirstKey, 3)
 	RegisterCommand("Decr", execDecr, writeFirstKey, rollbackFirstKey, 2)
 	RegisterCommand("DecrBy", execDecrBy, writeFirstKey, rollbackFirstKey, 3)
+	RegisterCommand("StrLen", execStrLen, readFirstKey, nil, 2)
+	RegisterCommand("Append", execAppend, writeFirstKey, rollbackFirstKey, 3)
 }
diff --git a/string_test.go b/string_test.go
index bf3d9cb..90a447b 100644
--- a/string_test.go
+++ b/string_test.go
@@ -315,3 +315,60 @@ func TestMSetNX(t *testing.T) {
 	result = testDB.Exec(nil, utils.ToCmdLine2("MSETNX", args[0:4]...))
 	asserts.AssertIntReply(t, result, 0)
 }
+
+func TestStrLen(t *testing.T) {
+	testDB.Flush()
+	key := utils.RandString(10)
+	testDB.Exec(nil, utils.ToCmdLine2("SET", key, key))
+
+	actual := testDB.Exec(nil, utils.ToCmdLine("StrLen", key))
+	len, ok := actual.(*reply.IntReply)
+	if !ok {
+		t.Errorf("expect int bulk reply, get: %s", string(actual.ToBytes()))
+		return
+	}
+	asserts.AssertIntReply(t, len, 10)
+}
+
+func TestStrLen_KeyNotExist(t *testing.T) {
+	testDB.Flush()
+	key := utils.RandString(10)
+
+	actual := testDB.Exec(nil, utils.ToCmdLine("StrLen", key))
+	result, ok := actual.(*reply.IntReply)
+	if !ok {
+		t.Errorf("expect null bulk reply, get: %s", string(actual.ToBytes()))
+		return
+	}
+
+	asserts.AssertIntReply(t, result, 0)
+}
+
+func TestAppend_KeyExist(t *testing.T) {
+	testDB.Flush()
+	key := utils.RandString(10)
+	key2 := utils.RandString(10)
+	testDB.Exec(nil, utils.ToCmdLine2("SET", key, key))
+
+	actual := testDB.Exec(nil, utils.ToCmdLine("Append", key, key2))
+	val, ok := actual.(*reply.IntReply)
+	if !ok {
+		t.Errorf("expect nil bulk reply, get: %s", string(actual.ToBytes()))
+		return
+	}
+	asserts.AssertIntReply(t, val, len(key)*2)
+}
+
+func TestAppend_KeyNotExist(t *testing.T) {
+	testDB.Flush()
+	key := utils.RandString(10)
+
+	actual := testDB.Exec(nil, utils.ToCmdLine("Append", key, key))
+	val, ok := actual.(*reply.IntReply)
+	if !ok {
+		t.Errorf("expect nil bulk reply, get: %s", string(actual.ToBytes()))
+		return
+	}
+	asserts.AssertIntReply(t, val, len(key))
+}
+