diff --git a/aof/aof.go b/aof/aof.go
index e72e840..bfe02a1 100644
--- a/aof/aof.go
+++ b/aof/aof.go
@@ -61,6 +61,8 @@ type Persister struct {
 	pausingAof sync.Mutex
 	currentDB  int
 	listeners  map[Listener]struct{}
+	// reuse cmdLine buffer
+	buffer []CmdLine
 }
 
 // NewPersister creates a new aof.Persister
@@ -70,6 +72,7 @@ func NewPersister(db database.DBEngine, filename string, load bool, fsync string
 	persister.aofFsync = strings.ToLower(fsync)
 	persister.db = db
 	persister.tmpDBMaker = tmpDBMaker
+	persister.currentDB = 0
 	if load {
 		persister.LoadAof(0)
 	}
@@ -100,20 +103,6 @@ func (persister *Persister) RemoveListener(listener Listener) {
 	delete(persister.listeners, listener)
 }
 
-var wgPool = sync.Pool{
-	New: func() interface{} {
-		return &sync.WaitGroup{}
-	},
-}
-
-func getWg() *sync.WaitGroup {
-	return wgPool.Get().(*sync.WaitGroup)
-}
-
-func returnWg(wg *sync.WaitGroup) {
-	wgPool.Put(wg)
-}
-
 // SaveCmdLine send command to aof goroutine through channel
 func (persister *Persister) SaveCmdLine(dbIndex int, cmdLine CmdLine) {
 	// aofChan will be set as nil temporarily during load aof see Persister.LoadAof
@@ -121,16 +110,12 @@ func (persister *Persister) SaveCmdLine(dbIndex int, cmdLine CmdLine) {
 		return
 	}
 	if persister.aofFsync == FsyncAlways {
-		// use WaitGroup to wait for saving finished
-		wg := getWg()
-		defer returnWg(wg)
-		wg.Add(1)
-		persister.aofChan <- &payload{
+		p := &payload{
 			cmdLine: cmdLine,
 			dbIndex: dbIndex,
-			wg:      wg,
 		}
-		wg.Wait()
+		persister.writeAof(p)
+		return
 	}
 	persister.aofChan <- &payload{
 		cmdLine: cmdLine,
@@ -140,46 +125,42 @@ func (persister *Persister) SaveCmdLine(dbIndex int, cmdLine CmdLine) {
 
 // listenCmd listen aof channel and write into file
 func (persister *Persister) listenCmd() {
-	// serialized execution
-	var cmdLines []CmdLine
-	persister.currentDB = 0
 	for p := range persister.aofChan {
-		cmdLines = cmdLines[:0]     // reuse underlying array
-		persister.pausingAof.Lock() // prevent other goroutines from pausing aof
-		// ensure aof is in the right database
-		if p.dbIndex != persister.currentDB {
-			// select db
-			selectCmd := utils.ToCmdLine("SELECT", strconv.Itoa(p.dbIndex))
-			cmdLines = append(cmdLines, selectCmd)
-			data := protocol.MakeMultiBulkReply(selectCmd).ToBytes()
-			_, err := persister.aofFile.Write(data)
-			if err != nil {
-				logger.Warn(err)
-				persister.pausingAof.Unlock()
-				continue // skip this command
-			}
-			persister.currentDB = p.dbIndex
-		}
-		// save command
-		data := protocol.MakeMultiBulkReply(p.cmdLine).ToBytes()
-		cmdLines = append(cmdLines, p.cmdLine)
+		persister.writeAof(p)
+	}
+	persister.aofFinished <- struct{}{}
+}
+
+func (persister *Persister) writeAof(p *payload) {
+	persister.buffer = persister.buffer[:0] // reuse underlying array
+	persister.pausingAof.Lock()             // prevent other goroutines from pausing aof
+	defer persister.pausingAof.Unlock()
+	// ensure aof is in the right database
+	if p.dbIndex != persister.currentDB {
+		// select db
+		selectCmd := utils.ToCmdLine("SELECT", strconv.Itoa(p.dbIndex))
+		persister.buffer = append(persister.buffer, selectCmd)
+		data := protocol.MakeMultiBulkReply(selectCmd).ToBytes()
 		_, err := persister.aofFile.Write(data)
 		if err != nil {
 			logger.Warn(err)
+			return // skip this command
 		}
-		for listener := range persister.listeners {
-			listener.Callback(cmdLines)
-		}
-		if persister.aofFsync == FsyncAlways {
-			_ = persister.aofFile.Sync()
-		}
-		if p.wg != nil {
-			p.wg.Done()
-		}
-		persister.pausingAof.Unlock()
-
+		persister.currentDB = p.dbIndex
+	}
+	// save command
+	data := protocol.MakeMultiBulkReply(p.cmdLine).ToBytes()
+	persister.buffer = append(persister.buffer, p.cmdLine)
+	_, err := persister.aofFile.Write(data)
+	if err != nil {
+		logger.Warn(err)
+	}
+	for listener := range persister.listeners {
+		listener.Callback(persister.buffer)
+	}
+	if persister.aofFsync == FsyncAlways {
+		_ = persister.aofFile.Sync()
 	}
-	persister.aofFinished <- struct{}{}
 }
 
 // LoadAof read aof file, can only be used before Persister.listenCmd started
@@ -231,6 +212,13 @@ func (persister *Persister) LoadAof(maxBytes int) {
 		if protocol.IsErrorReply(ret) {
 			logger.Error("exec err", string(ret.ToBytes()))
 		}
+		if strings.ToLower(string(r.Args[0])) == "select" {
+			// execSelect success, here must be no error
+			dbIndex, err := strconv.Atoi(string(r.Args[1]))
+			if err == nil {
+				persister.currentDB = dbIndex
+			}
+		}
 	}
 }
 
diff --git a/database/persistence_test.go b/database/persistence_test.go
index d8421d7..41a77c6 100644
--- a/database/persistence_test.go
+++ b/database/persistence_test.go
@@ -53,7 +53,8 @@ func TestServerFsyncAlways(t *testing.T) {
 	config.Properties.AppendFsync = aof.FsyncAlways
 	server := NewStandaloneServer()
 	conn := connection.NewFakeConn()
-	ret := server.Exec(conn, utils.ToCmdLine("set", "1", "1"))
+	server.Exec(conn, utils.ToCmdLine("del", "1"))
+	ret := server.Exec(conn, utils.ToCmdLine("incr", "1"))
 	asserts.AssertNotError(t, ret)
 	reader := NewStandaloneServer()
 	ret = reader.Exec(conn, utils.ToCmdLine("get", "1"))
@@ -71,7 +72,8 @@ func TestServerFsyncEverySec(t *testing.T) {
 	config.Properties.AppendFsync = aof.FsyncEverySec
 	server := NewStandaloneServer()
 	conn := connection.NewFakeConn()
-	ret := server.Exec(conn, utils.ToCmdLine("set", "1", "1"))
+	server.Exec(conn, utils.ToCmdLine("del", "1"))
+	ret := server.Exec(conn, utils.ToCmdLine("incr", "1"))
 	asserts.AssertNotError(t, ret)
 	time.Sleep(1500 * time.Millisecond)
 	reader := NewStandaloneServer()