diff --git a/internal/server/aof.go b/internal/server/aof.go
index 42a42946..afcb1f08 100644
--- a/internal/server/aof.go
+++ b/internal/server/aof.go
@@ -115,6 +115,8 @@ func commandErrIsFatal(err error) bool {
 	return true
 }
 
+// flushAOF flushes all aof buffer data to disk. Set sync to true to sync the
+// fsync the file.
 func (server *Server) flushAOF(sync bool) {
 	if len(server.aofbuf) > 0 {
 		_, err := server.aof.Write(server.aofbuf)
@@ -126,12 +128,15 @@ func (server *Server) flushAOF(sync bool) {
 				panic(err)
 			}
 		}
-		server.aofbuf = server.aofbuf[:0]
+		if cap(server.aofbuf) > 1024*1024*32 {
+			server.aofbuf = make([]byte, 0, 1024*1024*32)
+		} else {
+			server.aofbuf = server.aofbuf[:0]
+		}
 	}
 }
 
 func (server *Server) writeAOF(args []string, d *commandDetails) error {
-
 	if d != nil && !d.updated {
 		// just ignore writes if the command did not update
 		return nil
diff --git a/internal/server/dev.go b/internal/server/dev.go
index c1a2562d..85aa939a 100644
--- a/internal/server/dev.go
+++ b/internal/server/dev.go
@@ -74,17 +74,18 @@ func (c *Server) cmdMassInsert(msg *Message) (res resp.Value, err error) {
 	if err != nil {
 		return NOMessage, errInvalidArgument(snumPoints)
 	}
+
 	docmd := func(args []string) error {
+		c.mu.Lock()
+		defer c.mu.Unlock()
 		var nmsg Message
 		nmsg = *msg
 		nmsg._command = ""
 		nmsg.Args = args
-		var d commandDetails
-		_, d, err = c.command(&nmsg, nil)
+		_, d, err := c.command(&nmsg, nil)
 		if err != nil {
 			return err
 		}
-
 		return c.writeAOF(nmsg.Args, &d)
 
 	}
@@ -128,13 +129,15 @@ func (c *Server) cmdMassInsert(msg *Message) (res resp.Value, err error) {
 						strconv.FormatFloat(lon, 'f', -1, 64),
 					)
 				}
-				if err := docmd(values); err != nil {
+				err := docmd(values)
+				if err != nil {
 					log.Fatal(err)
 					return
 				}
 				atomic.AddUint64(&k, 1)
 				if j%1000 == 1000-1 {
-					log.Infof("massinsert: %s %d/%d", key, atomic.LoadUint64(&k), cols*objs)
+					log.Debugf("massinsert: %s %d/%d",
+						key, atomic.LoadUint64(&k), cols*objs)
 				}
 			}
 		}(key)
diff --git a/internal/server/server.go b/internal/server/server.go
index bf6c8287..9e163766 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -600,10 +600,7 @@ func (server *Server) backgroundSyncAOF() {
 		func() {
 			server.mu.Lock()
 			defer server.mu.Unlock()
-			if len(server.aofbuf) > 0 {
-				server.flushAOF(true)
-			}
-			server.aofbuf = nil
+			server.flushAOF(true)
 		}()
 	}
 }
@@ -831,8 +828,6 @@ func (server *Server) handleInputCommand(client *Client, msg *Message) error {
 	case "echo":
 	case "massinsert":
 		// dev operation
-		server.mu.Lock()
-		defer server.mu.Unlock()
 	case "sleep":
 		// dev operation
 		server.mu.RLock()