diff --git a/pkg/meta/tkv.go b/pkg/meta/tkv.go
index 666ba8f1694a..f5150fcec5c4 100644
--- a/pkg/meta/tkv.go
+++ b/pkg/meta/tkv.go
@@ -46,7 +46,7 @@ type kvtxn interface {
 	scan(begin, end []byte, keysOnly bool, handler func(k, v []byte) bool)
 	exist(prefix []byte) bool
 	set(key, value []byte)
-	append(key []byte, value []byte) []byte
+	append(key []byte, value []byte)
 	incrBy(key []byte, value int64) int64
 	delete(key []byte)
 }
@@ -3232,9 +3232,11 @@ func (m *kvMeta) LoadMeta(r io.Reader) error {
 		go func() {
 			defer wg.Done()
 			var buffer []*pair
+			var total int
 			for p := range kv {
 				buffer = append(buffer, p)
-				if len(buffer) >= batch {
+				total += len(p.key) + len(p.value)
+				if len(buffer) >= batch || total > 5<<20 {
 					err := m.txn(func(tx *kvTxn) error {
 						for _, p := range buffer {
 							tx.set(p.key, p.value)
@@ -3245,6 +3247,7 @@ func (m *kvMeta) LoadMeta(r io.Reader) error {
 						logger.Fatalf("write %d pairs: %s", len(buffer), err)
 					}
 					buffer = buffer[:0]
+					total = 0
 				}
 			}
 			if len(buffer) > 0 {
diff --git a/pkg/meta/tkv_badger.go b/pkg/meta/tkv_badger.go
index 69d2f300a4b5..432b692ba48d 100644
--- a/pkg/meta/tkv_badger.go
+++ b/pkg/meta/tkv_badger.go
@@ -112,10 +112,9 @@ func (tx *badgerTxn) set(key, value []byte) {
 	}
 }
 
-func (tx *badgerTxn) append(key []byte, value []byte) []byte {
+func (tx *badgerTxn) append(key []byte, value []byte) {
 	list := append(tx.get(key), value...)
 	tx.set(key, list)
-	return list
 }
 
 func (tx *badgerTxn) incrBy(key []byte, value int64) int64 {
diff --git a/pkg/meta/tkv_etcd.go b/pkg/meta/tkv_etcd.go
index 75534546ce85..63dad8189ed0 100644
--- a/pkg/meta/tkv_etcd.go
+++ b/pkg/meta/tkv_etcd.go
@@ -151,10 +151,9 @@ func (tx *etcdTxn) set(key, value []byte) {
 	}
 }
 
-func (tx *etcdTxn) append(key []byte, value []byte) []byte {
+func (tx *etcdTxn) append(key []byte, value []byte) {
 	new := append(tx.get(key), value...)
 	tx.set(key, new)
-	return new
 }
 
 func (tx *etcdTxn) incrBy(key []byte, value int64) int64 {
diff --git a/pkg/meta/tkv_fdb.go b/pkg/meta/tkv_fdb.go
index f98752ec300e..901117e66494 100644
--- a/pkg/meta/tkv_fdb.go
+++ b/pkg/meta/tkv_fdb.go
@@ -52,6 +52,7 @@ func newFdbClient(addr string) (tkvClient, error) {
 	if err != nil {
 		return nil, fmt.Errorf("open database: %s", err)
 	}
+	// TODO: database options
 	return withPrefix(&fdbClient{db}, append([]byte(u.Query().Get("prefix")), 0xFD)), nil
 }
 
@@ -74,6 +75,7 @@ func (c *fdbClient) scan(prefix []byte, handler func(key, value []byte)) error {
 	var done bool
 	for {
 		if _, err := c.client.ReadTransact(func(t fdb.ReadTransaction) (interface{}, error) {
+			// TODO:  t.Options().SetPriorityBatch()
 			snapshot := t.Snapshot()
 			iter := snapshot.GetRange(
 				fdb.KeyRange{Begin: begin, End: end},
@@ -113,7 +115,6 @@ func (c *fdbClient) reset(prefix []byte) error {
 }
 
 func (c *fdbClient) close() error {
-	// c = &fdbClient{}
 	return nil
 }
 
@@ -128,10 +129,13 @@ func (tx *fdbTxn) get(key []byte) []byte {
 }
 
 func (tx *fdbTxn) gets(keys ...[]byte) [][]byte {
-	ret := make([][]byte, len(keys))
+	fut := make([]fdb.FutureByteSlice, len(keys))
 	for i, key := range keys {
-		val := tx.Get(fdb.Key(key)).MustGet()
-		ret[i] = val
+		fut[i] = tx.Get(fdb.Key(key))
+	}
+	ret := make([][]byte, len(keys))
+	for i, f := range fut {
+		ret[i] = f.MustGet()
 	}
 	return ret
 }
@@ -158,13 +162,13 @@ func (tx *fdbTxn) set(key, value []byte) {
 	tx.Set(fdb.Key(key), value)
 }
 
-func (tx *fdbTxn) append(key []byte, value []byte) []byte {
+func (tx *fdbTxn) append(key []byte, value []byte) {
 	tx.AppendIfFits(fdb.Key(key), fdb.Key(value))
-	return tx.Get(fdb.Key(key)).MustGet()
 }
 
 func (tx *fdbTxn) incrBy(key []byte, value int64) int64 {
 	tx.Add(fdb.Key(key), packCounter(value))
+	// TODO: don't return new value if not needed
 	return parseCounter(tx.Get(fdb.Key(key)).MustGet())
 }
 
diff --git a/pkg/meta/tkv_mem.go b/pkg/meta/tkv_mem.go
index 11e5808b27e5..e7b2b3ebcc14 100644
--- a/pkg/meta/tkv_mem.go
+++ b/pkg/meta/tkv_mem.go
@@ -131,10 +131,9 @@ func (tx *memTxn) set(key, value []byte) {
 	tx.buffer[string(key)] = value
 }
 
-func (tx *memTxn) append(key []byte, value []byte) []byte {
+func (tx *memTxn) append(key []byte, value []byte) {
 	new := append(tx.get(key), value...)
 	tx.set(key, new)
-	return new
 }
 
 func (tx *memTxn) incrBy(key []byte, value int64) int64 {
diff --git a/pkg/meta/tkv_prefix.go b/pkg/meta/tkv_prefix.go
index 5bfe85d66851..16ddd3738960 100644
--- a/pkg/meta/tkv_prefix.go
+++ b/pkg/meta/tkv_prefix.go
@@ -60,8 +60,8 @@ func (tx *prefixTxn) set(key, value []byte) {
 	tx.kvTxn.set(tx.realKey(key), value)
 }
 
-func (tx *prefixTxn) append(key []byte, value []byte) []byte {
-	return tx.kvTxn.append(tx.realKey(key), value)
+func (tx *prefixTxn) append(key []byte, value []byte) {
+	tx.kvTxn.append(tx.realKey(key), value)
 }
 
 func (tx *prefixTxn) incrBy(key []byte, value int64) int64 {
diff --git a/pkg/meta/tkv_tikv.go b/pkg/meta/tkv_tikv.go
index 4804eb2a8e3e..c682bd7095be 100644
--- a/pkg/meta/tkv_tikv.go
+++ b/pkg/meta/tkv_tikv.go
@@ -146,10 +146,9 @@ func (tx *tikvTxn) set(key, value []byte) {
 	}
 }
 
-func (tx *tikvTxn) append(key []byte, value []byte) []byte {
+func (tx *tikvTxn) append(key []byte, value []byte) {
 	new := append(tx.get(key), value...)
 	tx.set(key, new)
-	return new
 }
 
 func (tx *tikvTxn) incrBy(key []byte, value int64) int64 {