diff --git a/pkg/apis/proto/source/v1/source.pb.go b/pkg/apis/proto/source/v1/source.pb.go
index 8e68737e..d2ac0624 100644
--- a/pkg/apis/proto/source/v1/source.pb.go
+++ b/pkg/apis/proto/source/v1/source.pb.go
@@ -1127,32 +1127,32 @@ var file_pkg_apis_proto_source_v1_source_proto_rawDesc = []byte{
 	0x66, 0x73, 0x65, 0x74, 0x18, 0x01, 0x20, 0x01, 0x28, 0x0c, 0x52, 0x06, 0x6f, 0x66, 0x66, 0x73,
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+	0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
diff --git a/pkg/apis/proto/source/v1/source.proto b/pkg/apis/proto/source/v1/source.proto
index 91e86ead..54a70230 100644
--- a/pkg/apis/proto/source/v1/source.proto
+++ b/pkg/apis/proto/source/v1/source.proto
@@ -19,7 +19,7 @@ service Source {
   // The caller (numa) expects the AckFn to be successful, and it does not expect any errors.
   // If there are some irrecoverable errors when the callee (UDSource) is processing the AckFn request,
   // then it is best to crash because there are no other retry mechanisms possible.
-  rpc AckFn(stream AckRequest) returns (AckResponse);
+  rpc AckFn(stream AckRequest) returns (stream AckResponse);
 
   // PendingFn returns the number of pending records at the user defined source.
   rpc PendingFn(google.protobuf.Empty) returns (PendingResponse);
diff --git a/pkg/apis/proto/source/v1/source_grpc.pb.go b/pkg/apis/proto/source/v1/source_grpc.pb.go
index fd9cd6bf..6348fe00 100644
--- a/pkg/apis/proto/source/v1/source_grpc.pb.go
+++ b/pkg/apis/proto/source/v1/source_grpc.pb.go
@@ -102,7 +102,7 @@ func (c *sourceClient) AckFn(ctx context.Context, opts ...grpc.CallOption) (Sour
 
 type Source_AckFnClient interface {
 	Send(*AckRequest) error
-	CloseAndRecv() (*AckResponse, error)
+	Recv() (*AckResponse, error)
 	grpc.ClientStream
 }
 
@@ -114,10 +114,7 @@ func (x *sourceAckFnClient) Send(m *AckRequest) error {
 	return x.ClientStream.SendMsg(m)
 }
 
-func (x *sourceAckFnClient) CloseAndRecv() (*AckResponse, error) {
-	if err := x.ClientStream.CloseSend(); err != nil {
-		return nil, err
-	}
+func (x *sourceAckFnClient) Recv() (*AckResponse, error) {
 	m := new(AckResponse)
 	if err := x.ClientStream.RecvMsg(m); err != nil {
 		return nil, err
@@ -242,7 +239,7 @@ func _Source_AckFn_Handler(srv interface{}, stream grpc.ServerStream) error {
 }
 
 type Source_AckFnServer interface {
-	SendAndClose(*AckResponse) error
+	Send(*AckResponse) error
 	Recv() (*AckRequest, error)
 	grpc.ServerStream
 }
@@ -251,7 +248,7 @@ type sourceAckFnServer struct {
 	grpc.ServerStream
 }
 
-func (x *sourceAckFnServer) SendAndClose(m *AckResponse) error {
+func (x *sourceAckFnServer) Send(m *AckResponse) error {
 	return x.ServerStream.SendMsg(m)
 }
 
@@ -347,6 +344,7 @@ var Source_ServiceDesc = grpc.ServiceDesc{
 		{
 			StreamName:    "AckFn",
 			Handler:       _Source_AckFn_Handler,
+			ServerStreams: true,
 			ClientStreams: true,
 		},
 	},
diff --git a/pkg/sourcer/service.go b/pkg/sourcer/service.go
index 6dd6a05d..72fe58e8 100644
--- a/pkg/sourcer/service.go
+++ b/pkg/sourcer/service.go
@@ -79,10 +79,11 @@ func (fs *Service) ReadFn(stream sourcepb.Source_ReadFnServer) error {
 			// Receive read requests from the stream
 			req, err := stream.Recv()
 			if err == io.EOF {
+				log.Printf("end of read stream")
 				return
 			}
 			if err != nil {
-				log.Printf("error receiving from stream: %v", err)
+				log.Printf("error receiving from read stream: %v", err)
 				errCh <- err
 				return
 			}
@@ -172,12 +173,11 @@ func (fs *Service) AckFn(stream sourcepb.Source_AckFnServer) error {
 		// Receive ack requests from the stream
 		req, err := stream.Recv()
 		if err == io.EOF {
-			return stream.SendAndClose(&sourcepb.AckResponse{
-				Result: &sourcepb.AckResponse_Result{},
-			})
+			log.Printf("end of ack stream")
+			return nil
 		}
 		if err != nil {
-			log.Printf("error receiving from stream: %v", err)
+			log.Printf("error receiving from ack stream: %v", err)
 			return err
 		}
 
@@ -185,6 +185,17 @@ func (fs *Service) AckFn(stream sourcepb.Source_AckFnServer) error {
 			offset: NewOffset(req.Request.Offset.GetOffset(), req.Request.Offset.GetPartitionId()),
 		}
 		fs.Source.Ack(ctx, &request)
+
+		// Send ack response
+		ackResponse := &sourcepb.AckResponse{
+			Result: &sourcepb.AckResponse_Result{
+				Success: &emptypb.Empty{},
+			},
+		}
+		if err := stream.Send(ackResponse); err != nil {
+			log.Printf("error sending ack response: %v", err)
+			return err
+		}
 	}
 }
 
diff --git a/pkg/sourcer/service_test.go b/pkg/sourcer/service_test.go
index cee11cc8..92bbefdf 100644
--- a/pkg/sourcer/service_test.go
+++ b/pkg/sourcer/service_test.go
@@ -117,8 +117,9 @@ func (te *ReadFnServerErrTest) Context() context.Context {
 }
 
 type AckFnServerTest struct {
-	ctx     context.Context
-	offsets []*sourcepb.Offset
+	ctx       context.Context
+	offsets   []*sourcepb.Offset
+	responses []*sourcepb.AckResponse
 	grpc.ServerStream
 	index int
 }
@@ -136,20 +137,22 @@ func (a *AckFnServerTest) Recv() (*sourcepb.AckRequest, error) {
 	}, nil
 }
 
+func (a *AckFnServerTest) Send(response *sourcepb.AckResponse) error {
+	a.responses = append(a.responses, response)
+	return nil
+}
+
 func NewAckFnServerTest(
 	ctx context.Context,
 	offsets []*sourcepb.Offset,
 ) *AckFnServerTest {
 	return &AckFnServerTest{
-		ctx:     ctx,
-		offsets: offsets,
+		ctx:       ctx,
+		offsets:   offsets,
+		responses: make([]*sourcepb.AckResponse, 0),
 	}
 }
 
-func (a *AckFnServerTest) SendAndClose(*sourcepb.AckResponse) error {
-	return nil
-}
-
 func (a *AckFnServerTest) Context() context.Context {
 	return a.ctx
 }
@@ -269,6 +272,18 @@ func TestService_AckFn(t *testing.T) {
 
 	err := fs.AckFn(ackFnStream)
 	assert.NoError(t, err)
+
+	expectedResponses := []*sourcepb.AckResponse{
+		{
+			Result: &sourcepb.AckResponse_Result{
+				Success: &emptypb.Empty{},
+			},
+		},
+	}
+
+	if !reflect.DeepEqual(ackFnStream.responses, expectedResponses) {
+		t.Errorf("AckFn() responses = %v, want %v", ackFnStream.responses, expectedResponses)
+	}
 }
 
 func TestService_PendingFn(t *testing.T) {