diff --git a/docs/developer_guides/developer_guides.md b/docs/developer_guides/developer_guides.md
index 7f76b28eb2..c99995e5e5 100644
--- a/docs/developer_guides/developer_guides.md
+++ b/docs/developer_guides/developer_guides.md
@@ -204,7 +204,7 @@ type Timestamp uint64
 
 #### 4.2 Timestamp Oracle
 
-```
+```go
 type timestampOracle struct {
   client *etcd.Client // client of a reliable meta service, i.e. etcd client
   rootPath string // this timestampOracle's working root path on the reliable kv service
@@ -213,16 +213,29 @@ type timestampOracle struct {
   tso Timestamp // monotonically increasing timestamp
 }
 
-func (tso *timestampOracle) GetTimestamp(count uint32) ([]Timestamp, Status)
+func (tso *timestampOracle) GetTimestamp(count uint32) ([]Timestamp, error)
 
-func (tso *timestampOracle) saveTimestamp() Status
-func (tso *timestampOracle) loadTimestamp() Status
+func (tso *timestampOracle) saveTimestamp() error
+func (tso *timestampOracle) loadTimestamp() error
 ```
 
 
 
 #### 4.2 Timestamp Allocator
 
+```go
+type TimestampAllocator struct {
+  Alloc(count uint32) ([]Timestamp, error)
+}
+
+func (allocator *TimestampAllocator) Start() error
+func (allocator *TimestampAllocator) Close() error
+
+func NewTimestampAllocator() *TimestampAllocator
+```
+
+
+
 ###### 4.2.1 Batch Allocation of Timestamps
 
 ###### 4.2.2 Expiration of Timestamps
@@ -277,10 +290,10 @@ type GlobalParamsTable struct {
   params memoryKV
 }
 
-func (gparams *GlobalParamsTable) Save(key, value string) Status
-func (gparams *GlobalParamsTable) Load(key string) (string, Status)
-func (gparams *GlobalParamsTable) LoadRange(key, endKey string, limit int) ([]string, []string, Status)
-func (gparams *GlobalParamsTable) Remove(key string) Status
+func (gparams *GlobalParamsTable) Save(key, value string) error
+func (gparams *GlobalParamsTable) Load(key string) (string, error)
+func (gparams *GlobalParamsTable) LoadRange(key, endKey string, limit int) ([]string, []string, error)
+func (gparams *GlobalParamsTable) Remove(key string) error
 ```
 
 
@@ -300,41 +313,46 @@ type TsMsg interface {
   Type() MsgType
 }
 
-type TsMsgMarshaler interface {
-  Marshal(input *TsMsg) ([]byte, Status)
-  Unmarshal(input []byte) (*TsMsg, Status)
-}
-
 type MsgPack struct {
   BeginTs Timestamp
   EndTs Timestamp
   Msgs []*TsMsg
 }
 
+type TsMsgMarshaler interface {
+  Marshal(input *TsMsg) ([]byte, error)
+  Unmarshal(input []byte) (*TsMsg, error)
+}
+
 type MsgStream interface {
   SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
-  Produce(*MsgPack) Status
+  Produce(*MsgPack) error
   Consume() *MsgPack // message can be consumed exactly once
 }
 
+type HashFunc func(*MsgPack) map[int32]*MsgPack
+
 type PulsarMsgStream struct {
   client *pulsar.Client
-  produceChannels []string
-  consumeChannels []string
-  
+  msgHashFunc HashFunc // return a map from produceChannel idx to *MsgPack
+  producers []*pulsar.Producer
+  consumers []*pulsar.Consumer
   msgMarshaler *TsMsgMarshaler
   msgUnmarshaler *TsMsgMarshaler
 }
 
+func (ms *PulsarMsgStream) SetProducerChannels(channels []string)
+func (ms *PulsarMsgStream) SetConsumerChannels(channels []string)
 func (ms *PulsarMsgStream) SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
-func (ms *PulsarMsgStream) Produce(*MsgPack) Status
-func (ms *PulsarMsgStream) Consume() *MsgPack //return messages in one time tick
+func (ms *PulsarMsgStream) SetMsgHashFunc(hashFunc *HashFunc)
+func (ms *PulsarMsgStream) Produce(msgs *MsgPack) error
+func (ms *PulsarMsgStream) Consume() (*MsgPack, error) //return messages in one time tick
 
 type PulsarTtMsgStream struct {
   client *pulsar.Client
-  produceChannels []string
-  consumeChannels []string
-  
+  msgHashFunc (*MsgPack) map[int32]*MsgPack // return a map from produceChannel idx to *MsgPack
+  producers []*pulsar.Producer
+  consumers []*pulsar.Consumer
   msgMarshaler *TsMsgMarshaler
   msgUnmarshaler *TsMsgMarshaler
   inputBuf []*TsMsg
@@ -342,9 +360,27 @@ type PulsarTtMsgStream struct {
   msgPacks []*MsgPack
 }
 
-func (ms *PulsarTtMsgStream) SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
-func (ms *PulsarTtMsgStream) Produce(*MsgPack) Status
-func (ms *PulsarTtMsgStream) Consume() *MsgPack //return messages in one time tick
+func (ms *PulsarMsgStream) SetProducerChannels(channels []string)
+func (ms *PulsarMsgStream) SetConsumerChannels(channels []string)
+func (ms *PulsarMsgStream) SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
+func (ms *PulsarMsgStream) SetMsgHashFunc(hashFunc *HashFunc)
+func (ms *PulsarMsgStream) Produce(msgs *MsgPack) error
+func (ms *PulsarMsgStream) Consume() *MsgPack //return messages in one time tick
+```
+
+
+
+#### 5.4 ID Allocator
+
+```go
+type IdAllocator struct {
+  Alloc(count uint32) ([]int64, error)
+}
+
+func (allocator *IdAllocator) Start() error
+func (allocator *IdAllocator) Close() error
+
+func NewIdAllocator() *IdAllocator
 ```
 
 
@@ -353,17 +389,60 @@ func (ms *PulsarTtMsgStream) Consume() *MsgPack //return messages in one time ti
 
 ## 6. Proxy
 
-#### 6.1 Overview
+#### 6.1 Proxy Instance
 
-#### 3.1 Task
+```go
+type Proxy struct {
+  servicepb.UnimplementedMilvusServiceServer
+  masterClient mpb.MasterClient
+  
+  timeTick *timeTick
+  ttStream *MessageStream
+  scheduler *taskScheduler
+  tsAllocator *TimestampAllocator
+  ReqIdAllocator *IdAllocator
+  RowIdAllocator *IdAllocator
+  SegIdAssigner *segIdAssigner
+}
+
+func (proxy *Proxy) Start() error
+func NewProxy(ctx context.Context) *Proxy
+```
+
+
+
+#### Global Parameter Table
+
+```go
+type GlobalParamsTable struct {
+}
+func (*paramTable GlobalParamsTable) ProxyId() int64
+func (*paramTable GlobalParamsTable) ProxyAddress() string
+func (*paramTable GlobalParamsTable) MasterAddress() string
+func (*paramTable GlobalParamsTable) PulsarAddress() string
+func (*paramTable GlobalParamsTable) TimeTickTopic() string
+func (*paramTable GlobalParamsTable) InsertTopics() []string
+func (*paramTable GlobalParamsTable) QueryTopic() string
+func (*paramTable GlobalParamsTable) QueryResultTopics() []string
+func (*paramTable GlobalParamsTable) Init() error
+
+var ProxyParamTable GlobalParamsTable
+```
+
+
+
+
+
+#### 6.2 Task
 
 ``` go
 type task interface {
-  PreExecute() Status
-  Execute() Status
-  PostExecute() Status
-  WaitToFinish() Status
-  Notify() Status
+  Id() int64	// return ReqId
+  PreExecute() error
+  Execute() error
+  PostExecute() error
+  WaitToFinish() error
+  Notify() error
 }
 ```
 
@@ -377,11 +456,11 @@ type baseTask struct {
   ProxyId int64
 }
 
-func (task *baseTask) PreExecute() Status
-func (task *baseTask) Execute() Status
-func (task *baseTask) PostExecute() Status
-func (task *baseTask) WaitToFinish() Status
-func (task *baseTask) Notify() Status
+func (task *baseTask) PreExecute() error
+func (task *baseTask) Execute() error
+func (task *baseTask) PostExecute() error
+func (task *baseTask) WaitToFinish() error
+func (task *baseTask) Notify() error
 ```
 
 * Insert Task
@@ -396,34 +475,121 @@ type insertTask struct {
   rowBatch *RowBatch
 }
 
-func (task *InsertTask) Execute() Status
-func (task *InsertTask) WaitToFinish() Status
-func (task *InsertTask) Notify() Status
+func (task *InsertTask) Execute() error
+func (task *InsertTask) WaitToFinish() error
+func (task *InsertTask) Notify() error
 ```
 
 
 
 #### 6.2 Task Scheduler
 
+* Base Task Queue
+
+```go
+type baseTaskQueue struct {
+  unissuedTasks *List
+  activeTasks map[int64]*task
+  utLock sync.Mutex	// lock for UnissuedTasks
+  atLock sync.Mutex	// lock for ActiveTasks
+}
+func (queue *baseTaskQueue) AddUnissuedTask(task *task)
+func (queue *baseTaskQueue) FrontUnissuedTask() *task
+func (queue *baseTaskQueue) PopUnissuedTask(id int64) *task
+func (queue *baseTaskQueue) AddActiveTask(task *task)
+func (queue *baseTaskQueue) PopActiveTask(id int64) *task
+func (queue *baseTaskQueue) TaskDoneTest(ts Timestamp) bool
+```
+
+*AddUnissuedTask(task \*task)* will put a new task into *unissuedTasks*, while maintaining the list by timestamp order.
+
+*TaskDoneTest(ts Timestamp)* will check both *unissuedTasks* and *unissuedTasks*. If no task found before *ts*, then the function returns *true*, indicates that all the tasks before *ts* are completed.
+
+
+
+* Data Definition Task Queue
+
+```go
+type ddTaskQueue struct {
+  baseTaskQueue
+  lock sync.Mutex
+}
+func (queue *ddTaskQueue) Enqueue(task *task) error
+
+func newDdTaskQueue() *ddTaskQueue
+```
+
+Data definition tasks (i.e. *CreateCollectionTask*) will be put into *DdTaskQueue*. If a task is enqueued, *Enqueue(task \*task)* will set *Ts*, *ReqId*, *ProxyId*, then push it into *queue*. The timestamps of the enqueued tasks should be strictly monotonically increasing. As *Enqueue(task \*task)* will be called in parallel, setting timestamp and queue insertion need to be done atomically.
+
+
+
+* Data Manipulation Task Queue
+
+```go
+type dmTaskQueue struct {
+  baseTaskQueue
+}
+func (queue *dmTaskQueue) Enqueue(task *task) error
+
+func newDmTaskQueue() *dmTaskQueue
+```
+
+Insert tasks and delete tasks will be put into *DmTaskQueue*.
+
+If a *insertTask* is enqueued, *Enqueue(task \*task)* will set *Ts*, *ReqId*, *ProxyId*, *SegIdAssigner*, *RowIdAllocator*, then push it into *queue*. The *SegIdAssigner* and *RowIdAllocator* will later be used in the task's execution phase.
+
+
+
+* Data Query Task Queue
+
+```go
+type dqTaskQueue struct {
+  baseTaskQueue
+}
+func (queue *dqTaskQueue) Enqueue(task *task) error
+
+func newDqTaskQueue() *dqTaskQueue
+```
+
+Queries will be put into *DqTaskQueue*.
+
+
+
+* Task Scheduler
+
 ``` go
 type taskScheduler struct {
-  // definition tasks
-  ddTasks *task chan
-  // manipulation tasks
-  dmTasks *task chan
-  // query tasks
-  dqTasks *task chan
+  DdQueue *ddTaskQueue
+  DmQueue *dmTaskQueue
+  DqQueue *dqTaskQueue
   
   tsAllocator *TimestampAllocator
   ReqIdAllocator *IdAllocator
 }
 
-func (sched *taskScheduler) EnqueueDDTask(task *task) Status
-func (sched *taskScheduler) EnqueueDMTask(task *task) Status
-func (sched *taskScheduler) EnqueueDQTask(task *task) Status
+func (sched *taskScheduler) scheduleDdTask() *task
+func (sched *taskScheduler) scheduleDmTask() *task
+func (sched *taskScheduler) scheduleDqTask() *task
 
+func (sched *taskScheduler) Start() error
 func (sched *taskScheduler) TaskDoneTest(ts Timestamp) bool
 
+func newTaskScheduler(ctx context.Context, tsAllocator *TimestampAllocator, ReqIdAllocator *IdAllocator) *taskScheduler
+```
+
+*scheduleDdTask()* selects tasks in a FIFO manner, thus time order is garanteed.
+
+The policy of *scheduleDmTask()* should target on throughput, not tasks' time order.  Note that the time order of the tasks' execution will later be garanteed by the timestamp & time tick mechanism.
+
+The policy of *scheduleDqTask()* should target on throughput. It should also take visibility into consideration. For example, if an insert task and a query arrive in a same time tick and the query comes after insert, the query should be scheduled in the next tick thus the query can see the insert.
+
+*TaskDoneTest(ts Timestamp)* will check all the three task queues. If no task found before *ts*, then the function returns *true*, indicates that all the tasks before *ts* are completed.
+
+
+
+* Statistics
+
+```go
 // ActiveComponent interfaces
 func (sched *taskScheduler) Id() String
 func (sched *taskScheduler) Status() Status
@@ -443,20 +609,40 @@ message taskSchedulerHeartbeat {
 }
 ```
 
-* EnqueueDMTask
 
-  If a insertTask is enqueued, *EnqueueDDTask(task \*task)* will set *Ts*, *ReqId*, *ProxyId*, *SegIdAssigner*, *RowIdAllocator*, then push it into queue *dmTasks*. The *SegIdAssigner* and *RowIdAllocator* will later be used in the task's execution phase.
 
 #### 6.3 Time Tick
 
+* Time Tick
+
 ``` go
 type timeTick struct {
   lastTick Timestamp
   currentTick Timestamp
+  wallTick Timestamp
+  tickStep Timestamp
+  syncInterval Timestamp
+  
+  tsAllocator *TimestampAllocator
+  scheduler *taskScheduler
+  ttStream *MessageStream
+  
+  ctx context.Context
 }
 
-func (tt *timeTick) tick() Status
+func (tt *timeTick) Start() error
+func (tt *timeTick) synchronize() error
 
+func newTimeTick(ctx context.Context, tickStep Timestamp, syncInterval Timestamp, tsAllocator *TimestampAllocator, scheduler *taskScheduler, ttStream *MessageStream) *timeTick
+```
+
+*Start()* will enter a loop. On each *tickStep*, it tries to send a *TIME_TICK* typed *TsMsg* into *ttStream*. After each *syncInterval*, it sychronizes its *wallTick* with *tsAllocator* by calling *synchronize()*. When *currentTick + tickStep < wallTick* holds, it will update *currentTick* with *wallTick* on next tick. Otherwise, it will update *currentTick* with *currentTick + tickStep*.
+
+
+
+* Statistics
+
+```go
 // ActiveComponent interfaces
 func (tt *timeTick) ID() String
 func (tt *timeTick) Status() Status
@@ -473,74 +659,7 @@ message TimeTickHeartbeat {
 
 
 
-## 7. Message Stream
 
-#### 7.1 Overview
-
-
-
-#### 7.2 Message Stream
-
-``` go
-type TsMsg interface {
-  SetTs(ts Timestamp)
-  Ts() Timestamp
-}
-
-type MsgPack struct {
-  BeginTs Timestamp
-  EndTs Timestamp
-  Msgs []*TsMsg
-}
-
-type TsMsgMarshaler interface {
-  Marshal(input *TsMsg) ([]byte, Status)
-  Unmarshal(input []byte) (*TsMsg, Status)
-}
-
-type MsgStream interface {
-  SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
-  Produce(*MsgPack) Status
-  Consume() *MsgPack // message can be consumed exactly once
-}
-
-type HashFunc func(*MsgPack) map[int32]*MsgPack
-
-type PulsarMsgStream struct {
-  client *pulsar.Client
-  msgHashFunc HashFunc // return a map from produceChannel idx to *MsgPack
-  producers []*pulsar.Producer
-  consumers []*pulsar.Consumer
-  msgMarshaler *TsMsgMarshaler
-  msgUnmarshaler *TsMsgMarshaler
-}
-
-func (ms *PulsarMsgStream) SetProducerChannels(channels []string)
-func (ms *PulsarMsgStream) SetConsumerChannels(channels []string)
-func (ms *PulsarMsgStream) SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
-func (ms *PulsarMsgStream) SetMsgHashFunc(hashFunc *HashFunc)
-func (ms *PulsarMsgStream) Produce(msgs *MsgPack) Status
-func (ms *PulsarMsgStream) Consume() *MsgPack //return messages in one time tick
-
-type PulsarTtMsgStream struct {
-  client *pulsar.Client
-  msgHashFunc (*MsgPack) map[int32]*MsgPack // return a map from produceChannel idx to *MsgPack
-  producers []*pulsar.Producer
-  consumers []*pulsar.Consumer
-  msgMarshaler *TsMsgMarshaler
-  msgUnmarshaler *TsMsgMarshaler
-  inputBuf []*TsMsg
-  unsolvedBuf []*TsMsg
-  msgPacks []*MsgPack
-}
-
-func (ms *PulsarMsgStream) SetProducerChannels(channels []string)
-func (ms *PulsarMsgStream) SetConsumerChannels(channels []string)
-func (ms *PulsarMsgStream) SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
-func (ms *PulsarMsgStream) SetMsgHashFunc(hashFunc *HashFunc)
-func (ms *PulsarMsgStream) Produce(msgs *MsgPack) Status
-func (ms *PulsarMsgStream) Consume() *MsgPack //return messages in one time tick
-```
 
 
 
@@ -602,13 +721,13 @@ type Segment struct {
 type ManipulationReqUnmarshaler struct {}
 
 // implementations of MsgUnmarshaler interfaces
-func (unmarshaler *InsertMsgUnmarshaler) Unmarshal(input *pulsar.Message) (*TsMsg, Status)
+func (unmarshaler *InsertMsgUnmarshaler) Unmarshal(input *pulsar.Message) (*TsMsg, error)
 
 
 type QueryReqUnmarshaler struct {}
 
 // implementations of MsgUnmarshaler interfaces
-func (unmarshaler *QueryReqUnmarshaler) Unmarshal(input *pulsar.Message) (*TsMsg, Status)
+func (unmarshaler *QueryReqUnmarshaler) Unmarshal(input *pulsar.Message) (*TsMsg, error)
 ```
 
 
@@ -695,9 +814,9 @@ Master receives data definition requests via grpc. Each request (described by a
 type task interface {
   Type() ReqType
   Ts() Timestamp
-  Execute() Status
-  WaitToFinish() Status
-  Notify() Status
+  Execute() error
+  WaitToFinish() error
+  Notify() error
 }
 ```
 
@@ -712,9 +831,9 @@ type createCollectionTask struct {
 // Task interfaces
 func (task *createCollectionTask) Type() ReqType
 func (task *createCollectionTask) Ts() Timestamp
-func (task *createCollectionTask) Execute() Status
-func (task *createCollectionTask) Notify() Status
-func (task *createCollectionTask) WaitToFinish() Status
+func (task *createCollectionTask) Execute() error
+func (task *createCollectionTask) Notify() error
+func (task *createCollectionTask) WaitToFinish() error
 ```
 
 
@@ -726,7 +845,7 @@ type ddRequestScheduler struct {
   reqQueue *task chan
 }
 
-func (rs *ddRequestScheduler) Enqueue(task *task) Status
+func (rs *ddRequestScheduler) Enqueue(task *task) error
 func (rs *ddRequestScheduler) schedule() *task // implement scheduling policy
 ```
 
diff --git a/internal/master/kv/etcd_kv.go b/internal/kv/etcd_kv.go
similarity index 86%
rename from internal/master/kv/etcd_kv.go
rename to internal/kv/etcd_kv.go
index 67148f4571..baa0b275fc 100644
--- a/internal/master/kv/etcd_kv.go
+++ b/internal/kv/etcd_kv.go
@@ -5,9 +5,9 @@ import (
 	"path"
 	"time"
 
+	"github.com/pingcap/log"
 	"github.com/zilliztech/milvus-distributed/internal/errors"
 	"github.com/zilliztech/milvus-distributed/internal/util/etcdutil"
-	"github.com/pingcap/log"
 	"go.etcd.io/etcd/clientv3"
 	"go.uber.org/zap"
 )
@@ -21,24 +21,24 @@ var (
 	errTxnFailed = errors.New("failed to commit transaction")
 )
 
-type EtcdKVBase struct {
+type EtcdKV struct {
 	client   *clientv3.Client
 	rootPath string
 }
 
-// NewEtcdKVBase creates a new etcd kv.
-func NewEtcdKVBase(client *clientv3.Client, rootPath string) *EtcdKVBase {
-	return &EtcdKVBase{
+// NewEtcdKV creates a new etcd kv.
+func NewEtcdKV(client *clientv3.Client, rootPath string) *EtcdKV {
+	return &EtcdKV{
 		client:   client,
 		rootPath: rootPath,
 	}
 }
 
-func (kv *EtcdKVBase) Close() {
+func (kv *EtcdKV) Close() {
 	kv.client.Close()
 }
 
-func (kv *EtcdKVBase) LoadWithPrefix(key string) ([]string, []string) {
+func (kv *EtcdKV) LoadWithPrefix(key string) ([]string, []string) {
 	key = path.Join(kv.rootPath, key)
 	println("in loadWithPrefix,", key)
 	resp, err := etcdutil.EtcdKVGet(kv.client, key, clientv3.WithPrefix())
@@ -61,7 +61,7 @@ func (kv *EtcdKVBase) LoadWithPrefix(key string) ([]string, []string) {
 	return keys, values
 }
 
-func (kv *EtcdKVBase) Load(key string) (string, error) {
+func (kv *EtcdKV) Load(key string) (string, error) {
 	key = path.Join(kv.rootPath, key)
 
 	resp, err := etcdutil.EtcdKVGet(kv.client, key)
@@ -76,7 +76,7 @@ func (kv *EtcdKVBase) Load(key string) (string, error) {
 	return string(resp.Kvs[0].Value), nil
 }
 
-func (kv *EtcdKVBase) Save(key, value string) error {
+func (kv *EtcdKV) Save(key, value string) error {
 	key = path.Join(kv.rootPath, key)
 
 	txn := NewSlowLogTxn(kv.client)
@@ -91,7 +91,7 @@ func (kv *EtcdKVBase) Save(key, value string) error {
 	return nil
 }
 
-func (kv *EtcdKVBase) Remove(key string) error {
+func (kv *EtcdKV) Remove(key string) error {
 	key = path.Join(kv.rootPath, key)
 
 	txn := NewSlowLogTxn(kv.client)
@@ -106,13 +106,13 @@ func (kv *EtcdKVBase) Remove(key string) error {
 	return nil
 }
 
-func (kv *EtcdKVBase) Watch(key string) clientv3.WatchChan {
+func (kv *EtcdKV) Watch(key string) clientv3.WatchChan {
 	key = path.Join(kv.rootPath, key)
 	rch := kv.client.Watch(context.Background(), key)
 	return rch
 }
 
-func (kv *EtcdKVBase) WatchWithPrefix(key string) clientv3.WatchChan {
+func (kv *EtcdKV) WatchWithPrefix(key string) clientv3.WatchChan {
 	key = path.Join(kv.rootPath, key)
 	rch := kv.client.Watch(context.Background(), key, clientv3.WithPrefix())
 	return rch
diff --git a/internal/master/kv/kv.go b/internal/kv/kv.go
similarity index 100%
rename from internal/master/kv/kv.go
rename to internal/kv/kv.go
diff --git a/internal/master/controller/collection.go b/internal/master/controller/collection.go
index 15c0504694..63f38c5df9 100644
--- a/internal/master/controller/collection.go
+++ b/internal/master/controller/collection.go
@@ -9,7 +9,7 @@ import (
 	"github.com/zilliztech/milvus-distributed/internal/master/collection"
 	"github.com/zilliztech/milvus-distributed/internal/proto/schemapb"
 	"github.com/zilliztech/milvus-distributed/internal/master/id"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/master/segment"
 )
 
diff --git a/internal/master/controller/segment.go b/internal/master/controller/segment.go
index 65fcab0fdd..e3f2655c96 100644
--- a/internal/master/controller/segment.go
+++ b/internal/master/controller/segment.go
@@ -10,7 +10,7 @@ import (
 	"github.com/zilliztech/milvus-distributed/internal/master/collection"
 	"github.com/zilliztech/milvus-distributed/internal/master/id"
 	//"github.com/zilliztech/milvus-distributed/internal/master/informer"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/master/segment"
 )
 
diff --git a/internal/master/controller/segment_test.go b/internal/master/controller/segment_test.go
index 7c9fd1ed19..7c87cb5b28 100644
--- a/internal/master/controller/segment_test.go
+++ b/internal/master/controller/segment_test.go
@@ -6,7 +6,7 @@ import (
 	"time"
 
 	"github.com/zilliztech/milvus-distributed/internal/conf"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/proto/internalpb"
 	"go.etcd.io/etcd/clientv3"
 )
@@ -19,7 +19,7 @@ func newKvBase() kv.Base {
 		Endpoints:   []string{etcdAddr},
 		DialTimeout: 5 * time.Second,
 	})
-	kvbase := kv.NewEtcdKVBase(cli, conf.Config.Etcd.Rootpath)
+	kvbase := kv.NewEtcdKV(cli, conf.Config.Etcd.Rootpath)
 	return kvbase
 }
 
diff --git a/internal/master/master.go b/internal/master/master.go
index b09c2e9b59..c70f844be4 100644
--- a/internal/master/master.go
+++ b/internal/master/master.go
@@ -18,7 +18,7 @@ import (
 	"fmt"
 	"github.com/zilliztech/milvus-distributed/internal/conf"
 	"github.com/zilliztech/milvus-distributed/internal/master/informer"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/proto/internalpb"
 	"github.com/zilliztech/milvus-distributed/internal/proto/masterpb"
 	"github.com/zilliztech/milvus-distributed/internal/master/controller"
@@ -80,7 +80,7 @@ func newKvBase() kv.Base {
 		DialTimeout: 5 * time.Second,
 	})
 	//	defer cli.Close()
-	kvBase := kv.NewEtcdKVBase(cli, conf.Config.Etcd.Rootpath)
+	kvBase := kv.NewEtcdKV(cli, conf.Config.Etcd.Rootpath)
 	return kvBase
 }
 
diff --git a/internal/master/meta_table.go b/internal/master/meta_table.go
index 41cb4faefb..2d065b5d98 100644
--- a/internal/master/meta_table.go
+++ b/internal/master/meta_table.go
@@ -2,7 +2,7 @@ package master
 
 import (
 	"github.com/zilliztech/milvus-distributed/internal/errors"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/proto/etcdpb"
 )
 
diff --git a/internal/master/task.go b/internal/master/task.go
index 825d07122b..c0e54bb1d7 100644
--- a/internal/master/task.go
+++ b/internal/master/task.go
@@ -2,7 +2,7 @@ package master
 
 import (
 	"context"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/proto/commonpb"
 	"github.com/zilliztech/milvus-distributed/internal/proto/internalpb"
 )
diff --git a/internal/reader/meta.go b/internal/reader/meta.go
index c0d8c00892..931079db8e 100644
--- a/internal/reader/meta.go
+++ b/internal/reader/meta.go
@@ -12,7 +12,7 @@ import (
 
 	"github.com/zilliztech/milvus-distributed/internal/conf"
 	"github.com/zilliztech/milvus-distributed/internal/master/collection"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/master/segment"
 	"go.etcd.io/etcd/clientv3"
 	"go.etcd.io/etcd/mvcc/mvccpb"
@@ -290,7 +290,7 @@ func (node *QueryNode) InitFromMeta() error {
 		DialTimeout: 5 * time.Second,
 	})
 	//defer cli.Close()
-	node.kvBase = kv.NewEtcdKVBase(cli, conf.Config.Etcd.Rootpath)
+	node.kvBase = kv.NewEtcdKV(cli, conf.Config.Etcd.Rootpath)
 	node.loadCollections()
 	node.loadSegments()
 	return nil
diff --git a/internal/reader/query_node.go b/internal/reader/query_node.go
index f2f741ba98..65b1510473 100644
--- a/internal/reader/query_node.go
+++ b/internal/reader/query_node.go
@@ -15,10 +15,11 @@ import "C"
 
 import (
 	"context"
-	"github.com/zilliztech/milvus-distributed/internal/master/kv"
+	"time"
+
+	"github.com/zilliztech/milvus-distributed/internal/kv"
 	"github.com/zilliztech/milvus-distributed/internal/msgclient"
 	msgPb "github.com/zilliztech/milvus-distributed/internal/proto/message"
-	"time"
 )
 
 type InsertData struct {
@@ -90,7 +91,7 @@ type QueryNode struct {
 	deletePreprocessData DeletePreprocessData
 	deleteData           DeleteData
 	insertData           InsertData
-	kvBase               *kv.EtcdKVBase
+	kvBase               *kv.EtcdKV
 	msgCounter           *MsgCounter
 	InsertLogs           []InsertLog
 }