diff --git a/cdc/kv/client_test.go b/cdc/kv/client_test.go
index 745b7d28224..b5a208ea765 100644
--- a/cdc/kv/client_test.go
+++ b/cdc/kv/client_test.go
@@ -29,6 +29,7 @@ import (
 	"github.com/pingcap/kvproto/pkg/metapb"
 	"github.com/pingcap/log"
 	"github.com/pingcap/ticdc/cdc/model"
+	cerror "github.com/pingcap/ticdc/pkg/errors"
 	"github.com/pingcap/ticdc/pkg/regionspan"
 	"github.com/pingcap/ticdc/pkg/retry"
 	"github.com/pingcap/ticdc/pkg/security"
@@ -1138,3 +1139,164 @@ func (s *etcdSuite) TestConnArray(c *check.C) {
 
 	ca.Close()
 }
+
+// TestPendingRegionError tests kv client should return an error when receiving
+// a new subscription (the first event of specific region) but the corresponding
+// region is not found in pending regions.
+func (s *etcdSuite) TestNoPendingRegionError(c *check.C) {
+	defer testleak.AfterTest(c)()
+	defer s.TearDownTest(c)
+	ctx, cancel := context.WithCancel(context.Background())
+	wg := &sync.WaitGroup{}
+
+	ch1 := make(chan *cdcpb.ChangeDataEvent, 10)
+	srv1 := newMockChangeDataService(c, ch1)
+	server1, addr1 := newMockService(ctx, c, srv1, wg)
+	defer func() {
+		close(ch1)
+		server1.Stop()
+		wg.Wait()
+	}()
+
+	cluster := mocktikv.NewCluster()
+	mvccStore := mocktikv.MustNewMVCCStore()
+	rpcClient, pdClient, err := mocktikv.NewTiKVAndPDClient(cluster, mvccStore, "")
+	c.Assert(err, check.IsNil)
+	pdClient = &mockPDClient{Client: pdClient, versionGen: defaultVersionGen}
+	kvStorage, err := tikv.NewTestTiKVStore(rpcClient, pdClient, nil, nil, 0)
+	c.Assert(err, check.IsNil)
+	defer kvStorage.Close() //nolint:errcheck
+
+	cluster.AddStore(1, addr1)
+	cluster.Bootstrap(3, []uint64{1}, []uint64{4}, 4)
+
+	baseAllocatedID := currentRequestID()
+	lockresolver := txnutil.NewLockerResolver(kvStorage.(tikv.Storage))
+	isPullInit := &mockPullerInit{}
+	cdcClient := NewCDCClient(ctx, pdClient, kvStorage.(tikv.Storage), &security.Credential{})
+	eventCh := make(chan *model.RegionFeedEvent, 10)
+	var wg2 sync.WaitGroup
+	wg2.Add(1)
+	go func() {
+		err := cdcClient.EventFeed(ctx, regionspan.ComparableSpan{Start: []byte("a"), End: []byte("b")}, 100, false, lockresolver, isPullInit, eventCh)
+		c.Assert(cerror.ErrNoPendingRegion.Equal(err), check.IsTrue)
+		cdcClient.Close() //nolint:errcheck
+		wg2.Done()
+	}()
+
+	// wait request id allocated with: new session, new request
+	waitRequestID(c, baseAllocatedID+1)
+	noPendingRegionEvent := &cdcpb.ChangeDataEvent{Events: []*cdcpb.Event{
+		{
+			RegionId:  3,
+			RequestId: currentRequestID() + 1, // an invalid request id
+			Event:     &cdcpb.Event_ResolvedTs{ResolvedTs: 100},
+		},
+	}}
+	ch1 <- noPendingRegionEvent
+	wg2.Wait()
+	cancel()
+}
+
+// TestDropStaleRequest tests kv client should drop an event if its request id is outdated.
+func (s *etcdSuite) TestDropStaleRequest(c *check.C) {
+	defer testleak.AfterTest(c)()
+	defer s.TearDownTest(c)
+	ctx, cancel := context.WithCancel(context.Background())
+	wg := &sync.WaitGroup{}
+
+	ch1 := make(chan *cdcpb.ChangeDataEvent, 10)
+	srv1 := newMockChangeDataService(c, ch1)
+	server1, addr1 := newMockService(ctx, c, srv1, wg)
+
+	defer func() {
+		close(ch1)
+		server1.Stop()
+		wg.Wait()
+	}()
+
+	cluster := mocktikv.NewCluster()
+	mvccStore := mocktikv.MustNewMVCCStore()
+	rpcClient, pdClient, err := mocktikv.NewTiKVAndPDClient(cluster, mvccStore, "")
+	c.Assert(err, check.IsNil)
+	pdClient = &mockPDClient{Client: pdClient, versionGen: defaultVersionGen}
+	kvStorage, err := tikv.NewTestTiKVStore(rpcClient, pdClient, nil, nil, 0)
+	c.Assert(err, check.IsNil)
+	defer kvStorage.Close() //nolint:errcheck
+
+	regionID := uint64(3)
+	cluster.AddStore(1, addr1)
+	cluster.Bootstrap(regionID, []uint64{1}, []uint64{4}, 4)
+
+	baseAllocatedID := currentRequestID()
+	lockresolver := txnutil.NewLockerResolver(kvStorage.(tikv.Storage))
+	isPullInit := &mockPullerInit{}
+	cdcClient := NewCDCClient(ctx, pdClient, kvStorage.(tikv.Storage), &security.Credential{})
+	eventCh := make(chan *model.RegionFeedEvent, 10)
+	wg.Add(1)
+	go func() {
+		err := cdcClient.EventFeed(ctx, regionspan.ComparableSpan{Start: []byte("a"), End: []byte("b")}, 100, false, lockresolver, isPullInit, eventCh)
+		c.Assert(errors.Cause(err), check.Equals, context.Canceled)
+		cdcClient.Close() //nolint:errcheck
+		wg.Done()
+	}()
+
+	// wait request id allocated with: new session, new request
+	waitRequestID(c, baseAllocatedID+1)
+
+	initialized := mockInitializedEvent(regionID, currentRequestID())
+	eventsAfterInit := &cdcpb.ChangeDataEvent{Events: []*cdcpb.Event{
+		{
+			RegionId:  regionID,
+			RequestId: currentRequestID(),
+			Event:     &cdcpb.Event_ResolvedTs{ResolvedTs: 120},
+		},
+		// This event will be dropped
+		{
+			RegionId:  regionID,
+			RequestId: currentRequestID() - 1,
+			Event:     &cdcpb.Event_ResolvedTs{ResolvedTs: 125},
+		},
+		{
+			RegionId:  regionID,
+			RequestId: currentRequestID(),
+			Event:     &cdcpb.Event_ResolvedTs{ResolvedTs: 130},
+		},
+	}}
+	expected := []*model.RegionFeedEvent{
+		{
+			Resolved: &model.ResolvedSpan{
+				Span:       regionspan.ComparableSpan{Start: []byte("a"), End: []byte("b")},
+				ResolvedTs: 100,
+			},
+			RegionID: regionID,
+		},
+		{
+			Resolved: &model.ResolvedSpan{
+				Span:       regionspan.ComparableSpan{Start: []byte("a"), End: []byte("b")},
+				ResolvedTs: 120,
+			},
+			RegionID: regionID,
+		},
+		{
+			Resolved: &model.ResolvedSpan{
+				Span:       regionspan.ComparableSpan{Start: []byte("a"), End: []byte("b")},
+				ResolvedTs: 130,
+			},
+			RegionID: regionID,
+		},
+	}
+
+	ch1 <- initialized
+	ch1 <- eventsAfterInit
+
+	for _, expectedEv := range expected {
+		select {
+		case event := <-eventCh:
+			c.Assert(event, check.DeepEquals, expectedEv)
+		case <-time.After(time.Second):
+			c.Errorf("expected event %v not received", expectedEv)
+		}
+	}
+	cancel()
+}