diff --git a/services/replicator/replicator.go b/services/replicator/replicator.go
index 7b372c0b..ff8735a5 100644
--- a/services/replicator/replicator.go
+++ b/services/replicator/replicator.go
@@ -39,6 +39,7 @@ import (
 	dconfig "github.com/uber/cherami-server/common/dconfigclient"
 	mm "github.com/uber/cherami-server/common/metadata"
 	"github.com/uber/cherami-server/common/metrics"
+	"github.com/uber/cherami-server/common/set"
 	storeStream "github.com/uber/cherami-server/stream"
 	"github.com/uber/cherami-thrift/.generated/go/admin"
 	"github.com/uber/cherami-thrift/.generated/go/metadata"
@@ -67,8 +68,7 @@ type (
 		storehostConn             map[string]*outConnection
 		storehostConnMutex        sync.RWMutex
 
-		knownCgExtents      map[string]struct{}
-		knownCgExtentsMutex sync.RWMutex
+		knownCgExtents set.Set
 
 		metadataReconciler MetadataReconciler
 	}
@@ -130,7 +130,7 @@ func NewReplicator(serviceName string, sVice common.SCommon, metadataClient meta
 		replicatorclientFactory:  replicatorClientFactory,
 		remoteReplicatorConn:     make(map[string]*outConnection),
 		storehostConn:            make(map[string]*outConnection),
-		knownCgExtents:           make(map[string]struct{}),
+		knownCgExtents:           set.NewConcurrent(0),
 	}
 
 	r.metaClient = mm.NewMetadataMetricsMgr(metadataClient, r.m3Client, r.logger)
@@ -1106,16 +1106,11 @@ func (r *Replicator) SetAckOffset(ctx thrift.Context, request *shared.SetAckOffs
 	})
 	r.m3Client.IncCounter(metrics.ReplicatorSetAckOffsetScope, metrics.ReplicatorRequests)
 
-	var cgExtentCreated bool
-	r.knownCgExtentsMutex.RLock()
-	_, cgExtentCreated = r.knownCgExtents[request.GetExtentUUID()]
-	r.knownCgExtentsMutex.RUnlock()
-
-	if !cgExtentCreated {
+	if !r.knownCgExtents.Contains(request.GetExtentUUID()) {
 		// make sure the cg extent is created locally before accepting the SetAckOffset call.
 		// otherwise SetAckOffset will create the cg extent entry with no store uuid or output host uuid
 		// and we may not be able to clean up the entry eventually.
-		extent, err := r.metaClient.ReadConsumerGroupExtent(nil, &metadata.ReadConsumerGroupExtentRequest{
+		_, err := r.metaClient.ReadConsumerGroupExtent(nil, &metadata.ReadConsumerGroupExtentRequest{
 			ConsumerGroupUUID: common.StringPtr(request.GetConsumerGroupUUID()),
 			ExtentUUID:        common.StringPtr(request.GetExtentUUID()),
 		})
@@ -1124,16 +1119,8 @@ func (r *Replicator) SetAckOffset(ctx thrift.Context, request *shared.SetAckOffs
 			r.m3Client.IncCounter(metrics.ReplicatorSetAckOffsetScope, metrics.ReplicatorFailures)
 			return err
 		}
-		if len(extent.GetExtent().GetStoreUUIDs()) < 1 {
-			err = fmt.Errorf(`empty store uuid from cg extent`)
-			lcllg.Error(`SetAckOffset: empty store uuid from cg extent`)
-			r.m3Client.IncCounter(metrics.ReplicatorSetAckOffsetScope, metrics.ReplicatorFailures)
-			return err
-		}
 
-		r.knownCgExtentsMutex.Lock()
-		r.knownCgExtents[request.GetExtentUUID()] = struct{}{}
-		r.knownCgExtentsMutex.Unlock()
+		r.knownCgExtents.Insert(request.GetExtentUUID())
 	}
 
 	err := r.metaClient.SetAckOffset(nil, request)
diff --git a/services/replicator/replicator_test.go b/services/replicator/replicator_test.go
index 045e0792..3b7afb2a 100644
--- a/services/replicator/replicator_test.go
+++ b/services/replicator/replicator_test.go
@@ -991,29 +991,6 @@ func (s *ReplicatorSuite) TestSetAckOffsetFailure_ReadExtentFail() {
 	s.mockMeta.AssertExpectations(s.T())
 }
 
-func (s *ReplicatorSuite) TestSetAckOffsetFailure_NoStoreUUID() {
-	repliator, _ := NewReplicator("replicator-test", s.mockService, s.mockMeta, s.mockReplicatorClientFactory, s.cfg)
-	cgUUID := uuid.New()
-	extentUUID := uuid.New()
-	ackLevel := int64(20)
-	req := &shared.SetAckOffsetRequest{
-		ConsumerGroupUUID: common.StringPtr(cgUUID),
-		ExtentUUID:        common.StringPtr(extentUUID),
-		AckLevelAddress:   common.Int64Ptr(ackLevel),
-	}
-
-	s.mockMeta.On("ReadConsumerGroupExtent", mock.Anything, mock.Anything).Return(&metadata.ReadConsumerGroupExtentResult_{
-		Extent: &shared.ConsumerGroupExtent{},
-	}, nil).Run(func(args mock.Arguments) {
-		req := args.Get(1).(*metadata.ReadConsumerGroupExtentRequest)
-		s.Equal(extentUUID, req.GetExtentUUID())
-		s.Equal(cgUUID, req.GetConsumerGroupUUID())
-	})
-	err := repliator.SetAckOffset(nil, req)
-	s.Error(err)
-	s.mockMeta.AssertExpectations(s.T())
-}
-
 func (s *ReplicatorSuite) TestRemoteSetAckOffsetFailed() {
 	repliator, _ := NewReplicator("replicator-test", s.mockService, s.mockMeta, s.mockReplicatorClientFactory, s.cfg)
 	extentUUID := uuid.New()