diff --git a/pkg/apis/proto/map/v1/map.pb.go b/pkg/apis/proto/map/v1/map.pb.go
index d47de582..c7708359 100644
--- a/pkg/apis/proto/map/v1/map.pb.go
+++ b/pkg/apis/proto/map/v1/map.pb.go
@@ -29,11 +29,10 @@ type MapRequest struct {
 	sizeCache     protoimpl.SizeCache
 	unknownFields protoimpl.UnknownFields
 
-	Keys      []string               `protobuf:"bytes,1,rep,name=keys,proto3" json:"keys,omitempty"`
-	Value     []byte                 `protobuf:"bytes,2,opt,name=value,proto3" json:"value,omitempty"`
-	EventTime *timestamppb.Timestamp `protobuf:"bytes,3,opt,name=event_time,json=eventTime,proto3" json:"event_time,omitempty"`
-	Watermark *timestamppb.Timestamp `protobuf:"bytes,4,opt,name=watermark,proto3" json:"watermark,omitempty"`
-	Headers   map[string]string      `protobuf:"bytes,5,rep,name=headers,proto3" json:"headers,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
+	Request *MapRequest_Request `protobuf:"bytes,1,opt,name=request,proto3" json:"request,omitempty"`
+	// This ID is used to uniquely identify a map request
+	Id        string     `protobuf:"bytes,2,opt,name=id,proto3" json:"id,omitempty"`
+	Handshake *Handshake `protobuf:"bytes,3,opt,name=handshake,proto3,oneof" json:"handshake,omitempty"`
 }
 
 func (x *MapRequest) Reset() {
@@ -68,39 +67,74 @@ func (*MapRequest) Descriptor() ([]byte, []int) {
 	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{0}
 }
 
-func (x *MapRequest) GetKeys() []string {
+func (x *MapRequest) GetRequest() *MapRequest_Request {
 	if x != nil {
-		return x.Keys
+		return x.Request
 	}
 	return nil
 }
 
-func (x *MapRequest) GetValue() []byte {
+func (x *MapRequest) GetId() string {
 	if x != nil {
-		return x.Value
+		return x.Id
 	}
-	return nil
+	return ""
 }
 
-func (x *MapRequest) GetEventTime() *timestamppb.Timestamp {
+func (x *MapRequest) GetHandshake() *Handshake {
 	if x != nil {
-		return x.EventTime
+		return x.Handshake
 	}
 	return nil
 }
 
-func (x *MapRequest) GetWatermark() *timestamppb.Timestamp {
-	if x != nil {
-		return x.Watermark
+// Handshake message between client and server to indicate the start of transmission.
+type Handshake struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// Required field indicating the start of transmission.
+	Sot bool `protobuf:"varint,1,opt,name=sot,proto3" json:"sot,omitempty"`
+}
+
+func (x *Handshake) Reset() {
+	*x = Handshake{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[1]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
 	}
-	return nil
 }
 
-func (x *MapRequest) GetHeaders() map[string]string {
+func (x *Handshake) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*Handshake) ProtoMessage() {}
+
+func (x *Handshake) ProtoReflect() protoreflect.Message {
+	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[1]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use Handshake.ProtoReflect.Descriptor instead.
+func (*Handshake) Descriptor() ([]byte, []int) {
+	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{1}
+}
+
+func (x *Handshake) GetSot() bool {
 	if x != nil {
-		return x.Headers
+		return x.Sot
 	}
-	return nil
+	return false
 }
 
 // *
@@ -111,12 +145,15 @@ type MapResponse struct {
 	unknownFields protoimpl.UnknownFields
 
 	Results []*MapResponse_Result `protobuf:"bytes,1,rep,name=results,proto3" json:"results,omitempty"`
+	// This ID is used to refer the responses to the request it corresponds to.
+	Id        string     `protobuf:"bytes,2,opt,name=id,proto3" json:"id,omitempty"`
+	Handshake *Handshake `protobuf:"bytes,3,opt,name=handshake,proto3,oneof" json:"handshake,omitempty"`
 }
 
 func (x *MapResponse) Reset() {
 	*x = MapResponse{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[1]
+		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[2]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -129,7 +166,7 @@ func (x *MapResponse) String() string {
 func (*MapResponse) ProtoMessage() {}
 
 func (x *MapResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[1]
+	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[2]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -142,7 +179,7 @@ func (x *MapResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use MapResponse.ProtoReflect.Descriptor instead.
 func (*MapResponse) Descriptor() ([]byte, []int) {
-	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{1}
+	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{2}
 }
 
 func (x *MapResponse) GetResults() []*MapResponse_Result {
@@ -152,6 +189,20 @@ func (x *MapResponse) GetResults() []*MapResponse_Result {
 	return nil
 }
 
+func (x *MapResponse) GetId() string {
+	if x != nil {
+		return x.Id
+	}
+	return ""
+}
+
+func (x *MapResponse) GetHandshake() *Handshake {
+	if x != nil {
+		return x.Handshake
+	}
+	return nil
+}
+
 // *
 // ReadyResponse is the health check result.
 type ReadyResponse struct {
@@ -165,7 +216,7 @@ type ReadyResponse struct {
 func (x *ReadyResponse) Reset() {
 	*x = ReadyResponse{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[2]
+		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[3]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -178,7 +229,7 @@ func (x *ReadyResponse) String() string {
 func (*ReadyResponse) ProtoMessage() {}
 
 func (x *ReadyResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[2]
+	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[3]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -191,7 +242,7 @@ func (x *ReadyResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use ReadyResponse.ProtoReflect.Descriptor instead.
 func (*ReadyResponse) Descriptor() ([]byte, []int) {
-	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{2}
+	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{3}
 }
 
 func (x *ReadyResponse) GetReady() bool {
@@ -201,6 +252,85 @@ func (x *ReadyResponse) GetReady() bool {
 	return false
 }
 
+type MapRequest_Request struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	Keys      []string               `protobuf:"bytes,1,rep,name=keys,proto3" json:"keys,omitempty"`
+	Value     []byte                 `protobuf:"bytes,2,opt,name=value,proto3" json:"value,omitempty"`
+	EventTime *timestamppb.Timestamp `protobuf:"bytes,3,opt,name=event_time,json=eventTime,proto3" json:"event_time,omitempty"`
+	Watermark *timestamppb.Timestamp `protobuf:"bytes,4,opt,name=watermark,proto3" json:"watermark,omitempty"`
+	Headers   map[string]string      `protobuf:"bytes,5,rep,name=headers,proto3" json:"headers,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
+}
+
+func (x *MapRequest_Request) Reset() {
+	*x = MapRequest_Request{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[4]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *MapRequest_Request) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*MapRequest_Request) ProtoMessage() {}
+
+func (x *MapRequest_Request) ProtoReflect() protoreflect.Message {
+	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[4]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use MapRequest_Request.ProtoReflect.Descriptor instead.
+func (*MapRequest_Request) Descriptor() ([]byte, []int) {
+	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{0, 0}
+}
+
+func (x *MapRequest_Request) GetKeys() []string {
+	if x != nil {
+		return x.Keys
+	}
+	return nil
+}
+
+func (x *MapRequest_Request) GetValue() []byte {
+	if x != nil {
+		return x.Value
+	}
+	return nil
+}
+
+func (x *MapRequest_Request) GetEventTime() *timestamppb.Timestamp {
+	if x != nil {
+		return x.EventTime
+	}
+	return nil
+}
+
+func (x *MapRequest_Request) GetWatermark() *timestamppb.Timestamp {
+	if x != nil {
+		return x.Watermark
+	}
+	return nil
+}
+
+func (x *MapRequest_Request) GetHeaders() map[string]string {
+	if x != nil {
+		return x.Headers
+	}
+	return nil
+}
+
 type MapResponse_Result struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -214,7 +344,7 @@ type MapResponse_Result struct {
 func (x *MapResponse_Result) Reset() {
 	*x = MapResponse_Result{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[4]
+		mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[6]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -227,7 +357,7 @@ func (x *MapResponse_Result) String() string {
 func (*MapResponse_Result) ProtoMessage() {}
 
 func (x *MapResponse_Result) ProtoReflect() protoreflect.Message {
-	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[4]
+	mi := &file_pkg_apis_proto_map_v1_map_proto_msgTypes[6]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -240,7 +370,7 @@ func (x *MapResponse_Result) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use MapResponse_Result.ProtoReflect.Descriptor instead.
 func (*MapResponse_Result) Descriptor() ([]byte, []int) {
-	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{1, 0}
+	return file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP(), []int{2, 0}
 }
 
 func (x *MapResponse_Result) GetKeys() []string {
@@ -273,48 +403,65 @@ var file_pkg_apis_proto_map_v1_map_proto_rawDesc = []byte{
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-	0x72, 0x6f, 0x74, 0x6f, 0x33,
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+	0x34, 0x0a, 0x09, 0x68, 0x61, 0x6e, 0x64, 0x73, 0x68, 0x61, 0x6b, 0x65, 0x18, 0x03, 0x20, 0x01,
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+	0x65, 0x79, 0x73, 0x12, 0x14, 0x0a, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x18, 0x02, 0x20, 0x01,
+	0x28, 0x0c, 0x52, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x12, 0x12, 0x0a, 0x04, 0x74, 0x61, 0x67,
+	0x73, 0x18, 0x03, 0x20, 0x03, 0x28, 0x09, 0x52, 0x04, 0x74, 0x61, 0x67, 0x73, 0x42, 0x0c, 0x0a,
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+	0x65, 0x61, 0x64, 0x79, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x12, 0x14, 0x0a, 0x05,
+	0x72, 0x65, 0x61, 0x64, 0x79, 0x18, 0x01, 0x20, 0x01, 0x28, 0x08, 0x52, 0x05, 0x72, 0x65, 0x61,
+	0x64, 0x79, 0x32, 0x75, 0x0a, 0x03, 0x4d, 0x61, 0x70, 0x12, 0x34, 0x0a, 0x05, 0x4d, 0x61, 0x70,
+	0x46, 0x6e, 0x12, 0x12, 0x2e, 0x6d, 0x61, 0x70, 0x2e, 0x76, 0x31, 0x2e, 0x4d, 0x61, 0x70, 0x52,
+	0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x1a, 0x13, 0x2e, 0x6d, 0x61, 0x70, 0x2e, 0x76, 0x31, 0x2e,
+	0x4d, 0x61, 0x70, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x28, 0x01, 0x30, 0x01, 0x12,
+	0x38, 0x0a, 0x07, 0x49, 0x73, 0x52, 0x65, 0x61, 0x64, 0x79, 0x12, 0x16, 0x2e, 0x67, 0x6f, 0x6f,
+	0x67, 0x6c, 0x65, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x62, 0x75, 0x66, 0x2e, 0x45, 0x6d, 0x70,
+	0x74, 0x79, 0x1a, 0x15, 0x2e, 0x6d, 0x61, 0x70, 0x2e, 0x76, 0x31, 0x2e, 0x52, 0x65, 0x61, 0x64,
+	0x79, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x42, 0x37, 0x5a, 0x35, 0x67, 0x69, 0x74,
+	0x68, 0x75, 0x62, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x6e, 0x75, 0x6d, 0x61, 0x70, 0x72, 0x6f, 0x6a,
+	0x2f, 0x6e, 0x75, 0x6d, 0x61, 0x66, 0x6c, 0x6f, 0x77, 0x2d, 0x67, 0x6f, 0x2f, 0x70, 0x6b, 0x67,
+	0x2f, 0x61, 0x70, 0x69, 0x73, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x2f, 0x6d, 0x61, 0x70, 0x2f,
+	0x76, 0x31, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
@@ -329,30 +476,35 @@ func file_pkg_apis_proto_map_v1_map_proto_rawDescGZIP() []byte {
 	return file_pkg_apis_proto_map_v1_map_proto_rawDescData
 }
 
-var file_pkg_apis_proto_map_v1_map_proto_msgTypes = make([]protoimpl.MessageInfo, 5)
+var file_pkg_apis_proto_map_v1_map_proto_msgTypes = make([]protoimpl.MessageInfo, 7)
 var file_pkg_apis_proto_map_v1_map_proto_goTypes = []any{
 	(*MapRequest)(nil),            // 0: map.v1.MapRequest
-	(*MapResponse)(nil),           // 1: map.v1.MapResponse
-	(*ReadyResponse)(nil),         // 2: map.v1.ReadyResponse
-	nil,                           // 3: map.v1.MapRequest.HeadersEntry
-	(*MapResponse_Result)(nil),    // 4: map.v1.MapResponse.Result
-	(*timestamppb.Timestamp)(nil), // 5: google.protobuf.Timestamp
-	(*emptypb.Empty)(nil),         // 6: google.protobuf.Empty
+	(*Handshake)(nil),             // 1: map.v1.Handshake
+	(*MapResponse)(nil),           // 2: map.v1.MapResponse
+	(*ReadyResponse)(nil),         // 3: map.v1.ReadyResponse
+	(*MapRequest_Request)(nil),    // 4: map.v1.MapRequest.Request
+	nil,                           // 5: map.v1.MapRequest.Request.HeadersEntry
+	(*MapResponse_Result)(nil),    // 6: map.v1.MapResponse.Result
+	(*timestamppb.Timestamp)(nil), // 7: google.protobuf.Timestamp
+	(*emptypb.Empty)(nil),         // 8: google.protobuf.Empty
 }
 var file_pkg_apis_proto_map_v1_map_proto_depIdxs = []int32{
-	5, // 0: map.v1.MapRequest.event_time:type_name -> google.protobuf.Timestamp
-	5, // 1: map.v1.MapRequest.watermark:type_name -> google.protobuf.Timestamp
-	3, // 2: map.v1.MapRequest.headers:type_name -> map.v1.MapRequest.HeadersEntry
-	4, // 3: map.v1.MapResponse.results:type_name -> map.v1.MapResponse.Result
-	0, // 4: map.v1.Map.MapFn:input_type -> map.v1.MapRequest
-	6, // 5: map.v1.Map.IsReady:input_type -> google.protobuf.Empty
-	1, // 6: map.v1.Map.MapFn:output_type -> map.v1.MapResponse
-	2, // 7: map.v1.Map.IsReady:output_type -> map.v1.ReadyResponse
-	6, // [6:8] is the sub-list for method output_type
-	4, // [4:6] is the sub-list for method input_type
-	4, // [4:4] is the sub-list for extension type_name
-	4, // [4:4] is the sub-list for extension extendee
-	0, // [0:4] is the sub-list for field type_name
+	4, // 0: map.v1.MapRequest.request:type_name -> map.v1.MapRequest.Request
+	1, // 1: map.v1.MapRequest.handshake:type_name -> map.v1.Handshake
+	6, // 2: map.v1.MapResponse.results:type_name -> map.v1.MapResponse.Result
+	1, // 3: map.v1.MapResponse.handshake:type_name -> map.v1.Handshake
+	7, // 4: map.v1.MapRequest.Request.event_time:type_name -> google.protobuf.Timestamp
+	7, // 5: map.v1.MapRequest.Request.watermark:type_name -> google.protobuf.Timestamp
+	5, // 6: map.v1.MapRequest.Request.headers:type_name -> map.v1.MapRequest.Request.HeadersEntry
+	0, // 7: map.v1.Map.MapFn:input_type -> map.v1.MapRequest
+	8, // 8: map.v1.Map.IsReady:input_type -> google.protobuf.Empty
+	2, // 9: map.v1.Map.MapFn:output_type -> map.v1.MapResponse
+	3, // 10: map.v1.Map.IsReady:output_type -> map.v1.ReadyResponse
+	9, // [9:11] is the sub-list for method output_type
+	7, // [7:9] is the sub-list for method input_type
+	7, // [7:7] is the sub-list for extension type_name
+	7, // [7:7] is the sub-list for extension extendee
+	0, // [0:7] is the sub-list for field type_name
 }
 
 func init() { file_pkg_apis_proto_map_v1_map_proto_init() }
@@ -374,7 +526,7 @@ func file_pkg_apis_proto_map_v1_map_proto_init() {
 			}
 		}
 		file_pkg_apis_proto_map_v1_map_proto_msgTypes[1].Exporter = func(v any, i int) any {
-			switch v := v.(*MapResponse); i {
+			switch v := v.(*Handshake); i {
 			case 0:
 				return &v.state
 			case 1:
@@ -386,6 +538,18 @@ func file_pkg_apis_proto_map_v1_map_proto_init() {
 			}
 		}
 		file_pkg_apis_proto_map_v1_map_proto_msgTypes[2].Exporter = func(v any, i int) any {
+			switch v := v.(*MapResponse); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_pkg_apis_proto_map_v1_map_proto_msgTypes[3].Exporter = func(v any, i int) any {
 			switch v := v.(*ReadyResponse); i {
 			case 0:
 				return &v.state
@@ -398,6 +562,18 @@ func file_pkg_apis_proto_map_v1_map_proto_init() {
 			}
 		}
 		file_pkg_apis_proto_map_v1_map_proto_msgTypes[4].Exporter = func(v any, i int) any {
+			switch v := v.(*MapRequest_Request); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_pkg_apis_proto_map_v1_map_proto_msgTypes[6].Exporter = func(v any, i int) any {
 			switch v := v.(*MapResponse_Result); i {
 			case 0:
 				return &v.state
@@ -410,13 +586,15 @@ func file_pkg_apis_proto_map_v1_map_proto_init() {
 			}
 		}
 	}
+	file_pkg_apis_proto_map_v1_map_proto_msgTypes[0].OneofWrappers = []any{}
+	file_pkg_apis_proto_map_v1_map_proto_msgTypes[2].OneofWrappers = []any{}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_pkg_apis_proto_map_v1_map_proto_rawDesc,
 			NumEnums:      0,
-			NumMessages:   5,
+			NumMessages:   7,
 			NumExtensions: 0,
 			NumServices:   1,
 		},
diff --git a/pkg/apis/proto/map/v1/map.proto b/pkg/apis/proto/map/v1/map.proto
index e93a9b01..76f8788d 100644
--- a/pkg/apis/proto/map/v1/map.proto
+++ b/pkg/apis/proto/map/v1/map.proto
@@ -9,7 +9,7 @@ package map.v1;
 
 service Map {
   // MapFn applies a function to each map request element.
-  rpc MapFn(MapRequest) returns (MapResponse);
+  rpc MapFn(stream MapRequest) returns (stream MapResponse);
 
   // IsReady is the heartbeat endpoint for gRPC.
   rpc IsReady(google.protobuf.Empty) returns (ReadyResponse);
@@ -19,11 +19,25 @@ service Map {
  * MapRequest represents a request element.
  */
 message MapRequest {
-  repeated string keys = 1;
-  bytes value = 2;
-  google.protobuf.Timestamp event_time = 3;
-  google.protobuf.Timestamp watermark = 4;
-  map<string, string> headers = 5;
+  message Request {
+    repeated string keys = 1;
+    bytes value = 2;
+    google.protobuf.Timestamp event_time = 3;
+    google.protobuf.Timestamp watermark = 4;
+    map<string, string> headers = 5;
+  }
+  Request request = 1;
+  // This ID is used to uniquely identify a map request
+  string id = 2;
+  optional Handshake handshake = 3;
+}
+
+/*
+ * Handshake message between client and server to indicate the start of transmission.
+ */
+message Handshake {
+  // Required field indicating the start of transmission.
+  bool sot = 1;
 }
 
 /**
@@ -36,6 +50,9 @@ message MapResponse {
     repeated string tags = 3;
   }
   repeated Result results = 1;
+  // This ID is used to refer the responses to the request it corresponds to.
+  string id = 2;
+  optional Handshake handshake = 3;
 }
 
 /**
diff --git a/pkg/apis/proto/map/v1/map_grpc.pb.go b/pkg/apis/proto/map/v1/map_grpc.pb.go
index d8552f56..0ee687b7 100644
--- a/pkg/apis/proto/map/v1/map_grpc.pb.go
+++ b/pkg/apis/proto/map/v1/map_grpc.pb.go
@@ -29,7 +29,7 @@ const (
 // For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
 type MapClient interface {
 	// MapFn applies a function to each map request element.
-	MapFn(ctx context.Context, in *MapRequest, opts ...grpc.CallOption) (*MapResponse, error)
+	MapFn(ctx context.Context, opts ...grpc.CallOption) (Map_MapFnClient, error)
 	// IsReady is the heartbeat endpoint for gRPC.
 	IsReady(ctx context.Context, in *emptypb.Empty, opts ...grpc.CallOption) (*ReadyResponse, error)
 }
@@ -42,14 +42,36 @@ func NewMapClient(cc grpc.ClientConnInterface) MapClient {
 	return &mapClient{cc}
 }
 
-func (c *mapClient) MapFn(ctx context.Context, in *MapRequest, opts ...grpc.CallOption) (*MapResponse, error) {
+func (c *mapClient) MapFn(ctx context.Context, opts ...grpc.CallOption) (Map_MapFnClient, error) {
 	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
-	out := new(MapResponse)
-	err := c.cc.Invoke(ctx, Map_MapFn_FullMethodName, in, out, cOpts...)
+	stream, err := c.cc.NewStream(ctx, &Map_ServiceDesc.Streams[0], Map_MapFn_FullMethodName, cOpts...)
 	if err != nil {
 		return nil, err
 	}
-	return out, nil
+	x := &mapMapFnClient{ClientStream: stream}
+	return x, nil
+}
+
+type Map_MapFnClient interface {
+	Send(*MapRequest) error
+	Recv() (*MapResponse, error)
+	grpc.ClientStream
+}
+
+type mapMapFnClient struct {
+	grpc.ClientStream
+}
+
+func (x *mapMapFnClient) Send(m *MapRequest) error {
+	return x.ClientStream.SendMsg(m)
+}
+
+func (x *mapMapFnClient) Recv() (*MapResponse, error) {
+	m := new(MapResponse)
+	if err := x.ClientStream.RecvMsg(m); err != nil {
+		return nil, err
+	}
+	return m, nil
 }
 
 func (c *mapClient) IsReady(ctx context.Context, in *emptypb.Empty, opts ...grpc.CallOption) (*ReadyResponse, error) {
@@ -67,7 +89,7 @@ func (c *mapClient) IsReady(ctx context.Context, in *emptypb.Empty, opts ...grpc
 // for forward compatibility
 type MapServer interface {
 	// MapFn applies a function to each map request element.
-	MapFn(context.Context, *MapRequest) (*MapResponse, error)
+	MapFn(Map_MapFnServer) error
 	// IsReady is the heartbeat endpoint for gRPC.
 	IsReady(context.Context, *emptypb.Empty) (*ReadyResponse, error)
 	mustEmbedUnimplementedMapServer()
@@ -77,8 +99,8 @@ type MapServer interface {
 type UnimplementedMapServer struct {
 }
 
-func (UnimplementedMapServer) MapFn(context.Context, *MapRequest) (*MapResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method MapFn not implemented")
+func (UnimplementedMapServer) MapFn(Map_MapFnServer) error {
+	return status.Errorf(codes.Unimplemented, "method MapFn not implemented")
 }
 func (UnimplementedMapServer) IsReady(context.Context, *emptypb.Empty) (*ReadyResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method IsReady not implemented")
@@ -96,22 +118,30 @@ func RegisterMapServer(s grpc.ServiceRegistrar, srv MapServer) {
 	s.RegisterService(&Map_ServiceDesc, srv)
 }
 
-func _Map_MapFn_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
-	in := new(MapRequest)
-	if err := dec(in); err != nil {
+func _Map_MapFn_Handler(srv interface{}, stream grpc.ServerStream) error {
+	return srv.(MapServer).MapFn(&mapMapFnServer{ServerStream: stream})
+}
+
+type Map_MapFnServer interface {
+	Send(*MapResponse) error
+	Recv() (*MapRequest, error)
+	grpc.ServerStream
+}
+
+type mapMapFnServer struct {
+	grpc.ServerStream
+}
+
+func (x *mapMapFnServer) Send(m *MapResponse) error {
+	return x.ServerStream.SendMsg(m)
+}
+
+func (x *mapMapFnServer) Recv() (*MapRequest, error) {
+	m := new(MapRequest)
+	if err := x.ServerStream.RecvMsg(m); err != nil {
 		return nil, err
 	}
-	if interceptor == nil {
-		return srv.(MapServer).MapFn(ctx, in)
-	}
-	info := &grpc.UnaryServerInfo{
-		Server:     srv,
-		FullMethod: Map_MapFn_FullMethodName,
-	}
-	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
-		return srv.(MapServer).MapFn(ctx, req.(*MapRequest))
-	}
-	return interceptor(ctx, in, info, handler)
+	return m, nil
 }
 
 func _Map_IsReady_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
@@ -139,15 +169,18 @@ var Map_ServiceDesc = grpc.ServiceDesc{
 	ServiceName: "map.v1.Map",
 	HandlerType: (*MapServer)(nil),
 	Methods: []grpc.MethodDesc{
-		{
-			MethodName: "MapFn",
-			Handler:    _Map_MapFn_Handler,
-		},
 		{
 			MethodName: "IsReady",
 			Handler:    _Map_IsReady_Handler,
 		},
 	},
-	Streams:  []grpc.StreamDesc{},
+	Streams: []grpc.StreamDesc{
+		{
+			StreamName:    "MapFn",
+			Handler:       _Map_MapFn_Handler,
+			ServerStreams: true,
+			ClientStreams: true,
+		},
+	},
 	Metadata: "pkg/apis/proto/map/v1/map.proto",
 }
diff --git a/pkg/mapper/examples/even_odd/go.mod b/pkg/mapper/examples/even_odd/go.mod
index 3c53ab1b..5d4b69a8 100644
--- a/pkg/mapper/examples/even_odd/go.mod
+++ b/pkg/mapper/examples/even_odd/go.mod
@@ -8,6 +8,7 @@ require github.com/numaproj/numaflow-go v0.8.1
 
 require (
 	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 // indirect
diff --git a/pkg/mapper/examples/even_odd/go.sum b/pkg/mapper/examples/even_odd/go.sum
index 09e06a2c..36997a49 100644
--- a/pkg/mapper/examples/even_odd/go.sum
+++ b/pkg/mapper/examples/even_odd/go.sum
@@ -8,6 +8,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
diff --git a/pkg/mapper/examples/flatmap/go.mod b/pkg/mapper/examples/flatmap/go.mod
index 24b28bb1..e4cdd7b8 100644
--- a/pkg/mapper/examples/flatmap/go.mod
+++ b/pkg/mapper/examples/flatmap/go.mod
@@ -8,6 +8,7 @@ require github.com/numaproj/numaflow-go v0.8.1
 
 require (
 	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 // indirect
diff --git a/pkg/mapper/examples/flatmap/go.sum b/pkg/mapper/examples/flatmap/go.sum
index 09e06a2c..36997a49 100644
--- a/pkg/mapper/examples/flatmap/go.sum
+++ b/pkg/mapper/examples/flatmap/go.sum
@@ -8,6 +8,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
diff --git a/pkg/mapper/examples/forward_message/go.mod b/pkg/mapper/examples/forward_message/go.mod
index 2b0abb6d..c1dc3be7 100644
--- a/pkg/mapper/examples/forward_message/go.mod
+++ b/pkg/mapper/examples/forward_message/go.mod
@@ -8,6 +8,7 @@ require github.com/numaproj/numaflow-go v0.8.1
 
 require (
 	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 // indirect
diff --git a/pkg/mapper/examples/forward_message/go.sum b/pkg/mapper/examples/forward_message/go.sum
index 09e06a2c..36997a49 100644
--- a/pkg/mapper/examples/forward_message/go.sum
+++ b/pkg/mapper/examples/forward_message/go.sum
@@ -8,6 +8,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
diff --git a/pkg/mapper/examples/retry/go.mod b/pkg/mapper/examples/retry/go.mod
index 9612714e..41a9d813 100644
--- a/pkg/mapper/examples/retry/go.mod
+++ b/pkg/mapper/examples/retry/go.mod
@@ -8,6 +8,7 @@ require github.com/numaproj/numaflow-go v0.8.1
 
 require (
 	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 // indirect
diff --git a/pkg/mapper/examples/retry/go.sum b/pkg/mapper/examples/retry/go.sum
index 09e06a2c..36997a49 100644
--- a/pkg/mapper/examples/retry/go.sum
+++ b/pkg/mapper/examples/retry/go.sum
@@ -8,6 +8,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
diff --git a/pkg/mapper/examples/tickgen/go.mod b/pkg/mapper/examples/tickgen/go.mod
index 0be651a1..988c6b88 100644
--- a/pkg/mapper/examples/tickgen/go.mod
+++ b/pkg/mapper/examples/tickgen/go.mod
@@ -8,6 +8,7 @@ require github.com/numaproj/numaflow-go v0.8.1
 
 require (
 	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 // indirect
diff --git a/pkg/mapper/examples/tickgen/go.sum b/pkg/mapper/examples/tickgen/go.sum
index 09e06a2c..36997a49 100644
--- a/pkg/mapper/examples/tickgen/go.sum
+++ b/pkg/mapper/examples/tickgen/go.sum
@@ -8,6 +8,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
diff --git a/pkg/mapper/server_test.go b/pkg/mapper/server_test.go
deleted file mode 100644
index baa94d4a..00000000
--- a/pkg/mapper/server_test.go
+++ /dev/null
@@ -1,116 +0,0 @@
-package mapper
-
-import (
-	"context"
-	"os"
-	"sync"
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/assert"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials/insecure"
-
-	mappb "github.com/numaproj/numaflow-go/pkg/apis/proto/map/v1"
-)
-
-func TestMapServer_Start(t *testing.T) {
-	socketFile, _ := os.CreateTemp("/tmp", "numaflow-test.sock")
-	defer func() {
-		_ = os.RemoveAll(socketFile.Name())
-	}()
-
-	serverInfoFile, _ := os.CreateTemp("/tmp", "numaflow-test-info")
-	defer func() {
-		_ = os.RemoveAll(serverInfoFile.Name())
-	}()
-
-	var mapHandler = MapperFunc(func(ctx context.Context, keys []string, d Datum) Messages {
-		msg := d.Value()
-		return MessagesBuilder().Append(NewMessage(msg).WithKeys([]string{keys[0] + "_test"}))
-	})
-	// note: using actual uds connection
-	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
-	defer cancel()
-	err := NewServer(mapHandler, WithSockAddr(socketFile.Name()), WithServerInfoFilePath(serverInfoFile.Name())).Start(ctx)
-	assert.NoError(t, err)
-}
-
-// tests the case where the server is shutdown gracefully when a panic occurs in the map handler
-func TestMapServer_GracefulShutdown(t *testing.T) {
-	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
-	defer cancel()
-
-	dir := t.TempDir()
-	socketFile, _ := os.Create(dir + "/test.sock")
-	defer func() {
-		_ = os.RemoveAll(socketFile.Name())
-	}()
-
-	serverInfoFile, _ := os.Create(dir + "/numaflow-test-info")
-	defer func() {
-		_ = os.RemoveAll(serverInfoFile.Name())
-	}()
-
-	var mapHandler = MapperFunc(func(ctx context.Context, keys []string, d Datum) Messages {
-		msg := d.Value()
-		if keys[0] == "key2" {
-			time.Sleep(20 * time.Millisecond)
-			panic("panic test")
-		}
-		time.Sleep(50 * time.Millisecond)
-		return MessagesBuilder().Append(NewMessage(msg).WithKeys([]string{keys[0] + "_test"}))
-	})
-
-	done := make(chan struct{})
-	go func() {
-		err := NewServer(mapHandler, WithSockAddr(socketFile.Name()), WithServerInfoFilePath(socketFile.Name())).Start(ctx)
-		assert.NoError(t, err)
-		close(done)
-	}()
-
-	// wait for the server to start
-	time.Sleep(10 * time.Millisecond)
-
-	// create a client
-	conn, err := grpc.NewClient(
-		"unix://"+socketFile.Name(),
-		grpc.WithTransportCredentials(insecure.NewCredentials()),
-	)
-	if err != nil {
-		t.Fatalf("Failed to dial server: %v", err)
-	}
-	defer conn.Close()
-
-	client := mappb.NewMapClient(conn)
-	// send two map requests with key1 and key2 as keys simultaneously
-	keys := []string{"key1", "key2"}
-	var wg sync.WaitGroup
-	for _, key := range keys {
-		wg.Add(1)
-		go func(key string) {
-			defer wg.Done()
-			req := &mappb.MapRequest{
-				Keys: []string{key},
-			}
-
-			resp, err := client.MapFn(ctx, req)
-			// since there is a panic in the map handler for key2, we should get an error
-			// other requests should be successful
-			if key == "key2" {
-				assert.Error(t, err)
-			} else {
-				assert.NoError(t, err)
-				assert.NotNil(t, resp)
-			}
-		}(key)
-	}
-
-	wg.Wait()
-	// wait for the server to shutdown gracefully because of the panic
-	select {
-	case <-ctx.Done():
-		t.Fatal("server did not shutdown gracefully")
-	case <-done:
-	}
-}
diff --git a/pkg/mapper/service.go b/pkg/mapper/service.go
index 235e372b..e9a537de 100644
--- a/pkg/mapper/service.go
+++ b/pkg/mapper/service.go
@@ -2,9 +2,12 @@ package mapper
 
 import (
 	"context"
+	"fmt"
+	"io"
 	"log"
 	"runtime/debug"
 
+	"golang.org/x/sync/errgroup"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 	"google.golang.org/protobuf/types/known/emptypb"
@@ -33,20 +36,111 @@ func (fs *Service) IsReady(context.Context, *emptypb.Empty) (*mappb.ReadyRespons
 }
 
 // MapFn applies a user defined function to each request element and returns a list of results.
-func (fs *Service) MapFn(ctx context.Context, d *mappb.MapRequest) (_ *mappb.MapResponse, err error) {
-	var hd = NewHandlerDatum(d.GetValue(), d.GetEventTime().AsTime(), d.GetWatermark().AsTime(), d.GetHeaders())
-	var elements []*mappb.MapResponse_Result
+func (fs *Service) MapFn(stream mappb.Map_MapFnServer) error {
+	// perform handshake with client before processing requests
+	if err := fs.performHandshake(stream); err != nil {
+		return err
+	}
+
+	ctx, cancel := context.WithCancel(stream.Context())
+	defer cancel()
+
+	// Use error group to manage goroutines, the grpCtx is cancelled when any of the
+	// goroutines return an error for the first time or the first time the wait returns.
+	g, grpCtx := errgroup.WithContext(ctx)
+
+	// Channel to collect responses
+	responseCh := make(chan *mappb.MapResponse, 500) // FIXME: identify the right buffer size
+	defer close(responseCh)
+
+	// Dedicated goroutine to send responses to the stream
+	g.Go(func() error {
+		for {
+			select {
+			case resp := <-responseCh:
+				if err := stream.Send(resp); err != nil {
+					log.Printf("failed to send response: %v", err)
+					return err
+				}
+			case <-grpCtx.Done():
+				return grpCtx.Err()
+			}
+		}
+	})
 
-	// Use defer and recover to handle panic
+	var readErr error
+	// Read requests from the stream and process them
+outer:
+	for {
+		select {
+		case <-grpCtx.Done():
+			break outer
+		default:
+		}
+		req, err := stream.Recv()
+		if err == io.EOF {
+			break outer
+		}
+		if err != nil {
+			log.Printf("Failed to receive request: %v", err)
+			readErr = err
+			// read loop is not part of the error group, so we need to cancel the context
+			// to signal the other goroutines to stop processing.
+			cancel()
+			break outer
+		}
+		g.Go(func() error {
+			return fs.handleRequest(grpCtx, req, responseCh)
+		})
+	}
+
+	// wait for all goroutines to finish
+	if err := g.Wait(); err != nil {
+		fs.shutdownCh <- struct{}{}
+		return status.Errorf(codes.Internal, "error processing requests: %v", err)
+	}
+
+	// check if there was an error while reading from the stream
+	if readErr != nil {
+		return status.Errorf(codes.Internal, readErr.Error())
+	}
+
+	return nil
+}
+
+// performHandshake handles the handshake logic at the start of the stream.
+func (fs *Service) performHandshake(stream mappb.Map_MapFnServer) error {
+	req, err := stream.Recv()
+	if err != nil {
+		return status.Errorf(codes.Internal, "failed to receive handshake: %v", err)
+	}
+	if req.GetHandshake() == nil || !req.GetHandshake().GetSot() {
+		return status.Errorf(codes.InvalidArgument, "invalid handshake")
+	}
+	handshakeResponse := &mappb.MapResponse{
+		Handshake: &mappb.Handshake{
+			Sot: true,
+		},
+	}
+	if err := stream.Send(handshakeResponse); err != nil {
+		return fmt.Errorf("sending handshake response to client over gRPC stream: %w", err)
+	}
+	return nil
+}
+
+// handleRequest processes each request and sends the response to the response channel.
+func (fs *Service) handleRequest(ctx context.Context, req *mappb.MapRequest, responseCh chan<- *mappb.MapResponse) (err error) {
 	defer func() {
 		if r := recover(); r != nil {
 			log.Printf("panic inside map handler: %v %v", r, string(debug.Stack()))
-			fs.shutdownCh <- struct{}{} // Send shutdown signal
-			err = status.Errorf(codes.Internal, "panic occurred in Mapper.Map: %v", r)
+			err = status.Errorf(codes.Internal, "panic inside map handler: %v", r)
 		}
 	}()
 
-	messages := fs.Mapper.Map(ctx, d.GetKeys(), hd)
+	request := req.GetRequest()
+	hd := NewHandlerDatum(request.GetValue(), request.GetEventTime().AsTime(), request.GetWatermark().AsTime(), request.GetHeaders())
+	messages := fs.Mapper.Map(ctx, request.GetKeys(), hd)
+	var elements []*mappb.MapResponse_Result
 	for _, m := range messages.Items() {
 		elements = append(elements, &mappb.MapResponse_Result{
 			Keys:  m.Keys(),
@@ -54,8 +148,14 @@ func (fs *Service) MapFn(ctx context.Context, d *mappb.MapRequest) (_ *mappb.Map
 			Tags:  m.Tags(),
 		})
 	}
-	datumList := &mappb.MapResponse{
+	resp := &mappb.MapResponse{
 		Results: elements,
+		Id:      req.GetId(),
+	}
+	select {
+	case responseCh <- resp:
+	case <-ctx.Done():
+		return ctx.Err()
 	}
-	return datumList, err
+	return nil
 }
diff --git a/pkg/mapper/service_test.go b/pkg/mapper/service_test.go
index 48e5a290..7ec939d1 100644
--- a/pkg/mapper/service_test.go
+++ b/pkg/mapper/service_test.go
@@ -2,26 +2,82 @@ package mapper
 
 import (
 	"context"
-	"reflect"
+	"errors"
+	"fmt"
+	"net"
 	"testing"
 	"time"
 
-	"google.golang.org/protobuf/types/known/timestamppb"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/test/bufconn"
+
+	proto "github.com/numaproj/numaflow-go/pkg/apis/proto/map/v1"
 
-	mappb "github.com/numaproj/numaflow-go/pkg/apis/proto/map/v1"
+	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
-func TestService_MapFn(t *testing.T) {
+func newTestServer(t *testing.T, register func(server *grpc.Server)) *grpc.ClientConn {
+	lis := bufconn.Listen(1024 * 1024)
+	t.Cleanup(func() {
+		_ = lis.Close()
+	})
+
+	server := grpc.NewServer()
+	t.Cleanup(func() {
+		server.Stop()
+	})
+
+	register(server)
+
+	errChan := make(chan error, 1)
+	go func() {
+		// t.Fatal should only be called from the goroutine running the test
+		if err := server.Serve(lis); err != nil {
+			errChan <- err
+		}
+	}()
+
+	dialer := func(context.Context, string) (net.Conn, error) {
+		return lis.Dial()
+	}
+
+	conn, err := grpc.NewClient("passthrough://", grpc.WithContextDialer(dialer), grpc.WithTransportCredentials(insecure.NewCredentials()))
+	t.Cleanup(func() {
+		_ = conn.Close()
+	})
+	if err != nil {
+		t.Fatalf("Creating new gRPC client connection: %v", err)
+	}
+
+	var grpcServerErr error
+	select {
+	case grpcServerErr = <-errChan:
+	case <-time.After(500 * time.Millisecond):
+		grpcServerErr = errors.New("gRPC server didn't start in 500ms")
+	}
+	if err != nil {
+		t.Fatalf("Failed to start gRPC server: %v", grpcServerErr)
+	}
+
+	return conn
+}
+
+func TestService_mapFn(t *testing.T) {
 	type args struct {
 		ctx context.Context
-		d   *mappb.MapRequest
+		d   *proto.MapRequest
 	}
+
 	tests := []struct {
 		name    string
 		handler Mapper
 		args    args
-		want    *mappb.MapResponse
-		wantErr bool
+		want    *proto.MapResponse
 	}{
 		{
 			name: "map_fn_forward_msg",
@@ -31,22 +87,23 @@ func TestService_MapFn(t *testing.T) {
 			}),
 			args: args{
 				ctx: context.Background(),
-				d: &mappb.MapRequest{
-					Keys:      []string{"client"},
-					Value:     []byte(`test`),
-					EventTime: timestamppb.New(time.Time{}),
-					Watermark: timestamppb.New(time.Time{}),
+				d: &proto.MapRequest{
+					Request: &proto.MapRequest_Request{
+						Keys:      []string{"client"},
+						Value:     []byte(`test`),
+						EventTime: timestamppb.New(time.Time{}),
+						Watermark: timestamppb.New(time.Time{}),
+					},
 				},
 			},
-			want: &mappb.MapResponse{
-				Results: []*mappb.MapResponse_Result{
+			want: &proto.MapResponse{
+				Results: []*proto.MapResponse_Result{
 					{
 						Keys:  []string{"client_test"},
 						Value: []byte(`test`),
 					},
 				},
 			},
-			wantErr: false,
 		},
 		{
 			name: "map_fn_forward_msg_forward_to_all",
@@ -56,21 +113,22 @@ func TestService_MapFn(t *testing.T) {
 			}),
 			args: args{
 				ctx: context.Background(),
-				d: &mappb.MapRequest{
-					Keys:      []string{"client"},
-					Value:     []byte(`test`),
-					EventTime: timestamppb.New(time.Time{}),
-					Watermark: timestamppb.New(time.Time{}),
+				d: &proto.MapRequest{
+					Request: &proto.MapRequest_Request{
+						Keys:      []string{"client"},
+						Value:     []byte(`test`),
+						EventTime: timestamppb.New(time.Time{}),
+						Watermark: timestamppb.New(time.Time{}),
+					},
 				},
 			},
-			want: &mappb.MapResponse{
-				Results: []*mappb.MapResponse_Result{
+			want: &proto.MapResponse{
+				Results: []*proto.MapResponse_Result{
 					{
 						Value: []byte(`test`),
 					},
 				},
 			},
-			wantErr: false,
 		},
 		{
 			name: "map_fn_forward_msg_drop_msg",
@@ -79,41 +137,157 @@ func TestService_MapFn(t *testing.T) {
 			}),
 			args: args{
 				ctx: context.Background(),
-				d: &mappb.MapRequest{
-					Keys:      []string{"client"},
-					Value:     []byte(`test`),
-					EventTime: timestamppb.New(time.Time{}),
-					Watermark: timestamppb.New(time.Time{}),
+				d: &proto.MapRequest{
+					Request: &proto.MapRequest_Request{
+						Keys:      []string{"client"},
+						Value:     []byte(`test`),
+						EventTime: timestamppb.New(time.Time{}),
+						Watermark: timestamppb.New(time.Time{}),
+					},
 				},
 			},
-			want: &mappb.MapResponse{
-				Results: []*mappb.MapResponse_Result{
+			want: &proto.MapResponse{
+				Results: []*proto.MapResponse_Result{
 					{
 						Tags:  []string{DROP},
-						Value: []byte{},
+						Value: nil,
 					},
 				},
 			},
-			wantErr: false,
 		},
 	}
+
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			fs := &Service{
+			svc := &Service{
 				Mapper: tt.handler,
 			}
-			// here's a trick for testing:
-			// because we are not using gRPC, we directly set a new incoming ctx
-			// instead of the regular outgoing context in the real gRPC connection.
-			ctx := context.Background()
-			got, err := fs.MapFn(ctx, tt.args.d)
-			if (err != nil) != tt.wantErr {
-				t.Errorf("MapFn() error = %v, wantErr %v", err, tt.wantErr)
-				return
-			}
-			if !reflect.DeepEqual(got, tt.want) {
-				t.Errorf("MapFn() got = %v, want %v", got, tt.want)
-			}
+
+			conn := newTestServer(t, func(server *grpc.Server) {
+				proto.RegisterMapServer(server, svc)
+			})
+
+			client := proto.NewMapClient(conn)
+			stream, err := client.MapFn(context.Background())
+			require.NoError(t, err, "Creating stream")
+
+			doHandshake(t, stream)
+
+			err = stream.Send(tt.args.d)
+			require.NoError(t, err, "Sending message over the stream")
+
+			got, err := stream.Recv()
+			require.NoError(t, err, "Receiving message from the stream")
+
+			assert.Equal(t, got.Results, tt.want.Results)
 		})
 	}
 }
+
+func doHandshake(t *testing.T, stream proto.Map_MapFnClient) {
+	t.Helper()
+	handshakeReq := &proto.MapRequest{
+		Handshake: &proto.Handshake{Sot: true},
+	}
+	err := stream.Send(handshakeReq)
+	require.NoError(t, err, "Sending handshake request to the stream")
+
+	handshakeResp, err := stream.Recv()
+	require.NoError(t, err, "Receiving handshake response")
+
+	require.Empty(t, handshakeResp.Results, "Invalid handshake response")
+	require.Empty(t, handshakeResp.Id, "Invalid handshake response")
+	require.NotNil(t, handshakeResp.Handshake, "Invalid handshake response")
+	require.True(t, handshakeResp.Handshake.Sot, "Invalid handshake response")
+}
+
+func TestService_MapFn_Multiple_Messages(t *testing.T) {
+	svc := &Service{
+		Mapper: MapperFunc(func(ctx context.Context, keys []string, datum Datum) Messages {
+			msg := datum.Value()
+			return MessagesBuilder().Append(NewMessage(msg).WithKeys([]string{keys[0] + "_test"}))
+		}),
+	}
+	conn := newTestServer(t, func(server *grpc.Server) {
+		proto.RegisterMapServer(server, svc)
+	})
+
+	client := proto.NewMapClient(conn)
+	stream, err := client.MapFn(context.Background())
+	require.NoError(t, err, "Creating stream")
+
+	doHandshake(t, stream)
+
+	const msgCount = 10
+	for i := 0; i < msgCount; i++ {
+		msg := proto.MapRequest{
+			Request: &proto.MapRequest_Request{
+				Keys:      []string{"client"},
+				Value:     []byte(fmt.Sprintf("test_%d", i)),
+				EventTime: timestamppb.New(time.Time{}),
+				Watermark: timestamppb.New(time.Time{}),
+			},
+		}
+		err = stream.Send(&msg)
+		require.NoError(t, err, "Sending message over the stream")
+	}
+	err = stream.CloseSend()
+	require.NoError(t, err, "Closing the send direction of the stream")
+
+	expectedResults := make([][]*proto.MapResponse_Result, msgCount)
+	for i := 0; i < msgCount; i++ {
+		expectedResults[i] = []*proto.MapResponse_Result{
+			{
+				Keys:  []string{"client_test"},
+				Value: []byte(fmt.Sprintf("test_%d", i)),
+			},
+		}
+	}
+
+	results := make([][]*proto.MapResponse_Result, msgCount)
+	for i := 0; i < msgCount; i++ {
+		got, err := stream.Recv()
+		require.NoError(t, err, "Receiving message from the stream")
+		results[i] = got.Results
+	}
+	require.ElementsMatch(t, results, expectedResults)
+}
+
+func TestService_MapFn_Panic(t *testing.T) {
+	svc := &Service{
+		Mapper: MapperFunc(func(ctx context.Context, keys []string, datum Datum) Messages {
+			panic("map failed")
+		}),
+		// panic in the transformer causes the server to send a shutdown signal to shutdownCh channel.
+		// The function that errgroup runs in a goroutine will be blocked until this shutdown signal is received somewhere else.
+		// Since we don't listen for shutdown signal in the tests, we use buffered channel to unblock the server function.
+		shutdownCh: make(chan<- struct{}, 1),
+	}
+	conn := newTestServer(t, func(server *grpc.Server) {
+		proto.RegisterMapServer(server, svc)
+	})
+
+	client := proto.NewMapClient(conn)
+	stream, err := client.MapFn(context.Background())
+	require.NoError(t, err, "Creating stream")
+
+	doHandshake(t, stream)
+
+	msg := proto.MapRequest{
+		Request: &proto.MapRequest_Request{
+			Keys:      []string{"client"},
+			Value:     []byte("test"),
+			EventTime: timestamppb.New(time.Time{}),
+			Watermark: timestamppb.New(time.Time{}),
+		},
+	}
+	err = stream.Send(&msg)
+	require.NoError(t, err, "Sending message over the stream")
+	err = stream.CloseSend()
+	require.NoError(t, err, "Closing the send direction of the stream")
+	_, err = stream.Recv()
+	require.Error(t, err, "Expected error while receiving message from the stream")
+	gotStatus, _ := status.FromError(err)
+	expectedStatus := status.Convert(status.Errorf(codes.Internal, "error processing requests: rpc error: code = Internal desc = panic inside map handler: map failed"))
+	require.Equal(t, expectedStatus, gotStatus)
+}
diff --git a/pkg/sideinput/examples/map_sideinput/udf/go.mod b/pkg/sideinput/examples/map_sideinput/udf/go.mod
index d783a749..78ff598e 100644
--- a/pkg/sideinput/examples/map_sideinput/udf/go.mod
+++ b/pkg/sideinput/examples/map_sideinput/udf/go.mod
@@ -11,6 +11,7 @@ require (
 
 require (
 	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 // indirect
diff --git a/pkg/sideinput/examples/map_sideinput/udf/go.sum b/pkg/sideinput/examples/map_sideinput/udf/go.sum
index 8ba4f4c5..249ac9a2 100644
--- a/pkg/sideinput/examples/map_sideinput/udf/go.sum
+++ b/pkg/sideinput/examples/map_sideinput/udf/go.sum
@@ -10,6 +10,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20220908164124-27713097b956/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
diff --git a/pkg/sideinput/examples/simple_sideinput/udf/go.mod b/pkg/sideinput/examples/simple_sideinput/udf/go.mod
index bbf5f7b3..8eef3bde 100644
--- a/pkg/sideinput/examples/simple_sideinput/udf/go.mod
+++ b/pkg/sideinput/examples/simple_sideinput/udf/go.mod
@@ -11,6 +11,7 @@ require (
 
 require (
 	golang.org/x/net v0.29.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
 	golang.org/x/sys v0.25.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240903143218-8af14fe29dc1 // indirect
diff --git a/pkg/sideinput/examples/simple_sideinput/udf/go.sum b/pkg/sideinput/examples/simple_sideinput/udf/go.sum
index 8ba4f4c5..249ac9a2 100644
--- a/pkg/sideinput/examples/simple_sideinput/udf/go.sum
+++ b/pkg/sideinput/examples/simple_sideinput/udf/go.sum
@@ -10,6 +10,8 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/net v0.29.0 h1:5ORfpBpCs4HzDYoodCDBbwHzdR5UrLBZ3sOnUJmFoHo=
 golang.org/x/net v0.29.0/go.mod h1:gLkgy8jTGERgjzMic6DS9+SP0ajcu6Xu3Orq/SpETg0=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20220908164124-27713097b956/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.25.0 h1:r+8e+loiHxRqhXVl6ML1nO3l1+oFoWbnlu2Ehimmi34=
 golang.org/x/sys v0.25.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
diff --git a/pkg/sourcetransformer/service.go b/pkg/sourcetransformer/service.go
index bbd91f19..c7212320 100644
--- a/pkg/sourcetransformer/service.go
+++ b/pkg/sourcetransformer/service.go
@@ -44,112 +44,123 @@ var errTransformerPanic = errors.New("transformer function panicked")
 // In addition to map function, SourceTransformFn also supports assigning a new event time to response.
 // SourceTransformFn can be used only at source vertex by source data transformer.
 func (fs *Service) SourceTransformFn(stream v1.SourceTransform_SourceTransformFnServer) error {
-	// handle panic
-	defer func() {
-		if r := recover(); r != nil {
-			log.Printf("panic inside sourcetransform handler: %v %v", r, string(debug.Stack()))
-			fs.shutdownCh <- struct{}{}
-		}
-	}()
-
-	req, err := stream.Recv()
-	if err != nil {
-		return fmt.Errorf("reading handshake message from stream: %w", err)
-	}
 
-	if req.Handshake == nil || !req.Handshake.Sot {
-		return fmt.Errorf("invalid handshake message: %+v", req)
+	// perform handshake with client before processing requests
+	if err := fs.performHandshake(stream); err != nil {
+		return err
 	}
 
-	handshakeResponse := &v1.SourceTransformResponse{
-		Handshake: &v1.Handshake{
-			Sot: true,
-		},
-	}
-	if err := stream.Send(handshakeResponse); err != nil {
-		return fmt.Errorf("sending handshake response to client over gRPC stream: %w", err)
-	}
+	ctx, cancel := context.WithCancel(stream.Context())
+	defer cancel()
 
-	ctx := stream.Context()
-	// We depend on grpContext to cancel all goroutines, since it will be automatically closed when the first function returns a non-nil error.
-	// This error will be caught later with grp.Wait()
+	// Use error group to manage goroutines, the grpCtx is cancelled when any of the
+	// goroutines return an error for the first time or the first time the wait returns.
 	grp, grpCtx := errgroup.WithContext(ctx)
 
 	senderCh := make(chan *v1.SourceTransformResponse, 500) // FIXME: identify the right buffer size
-	// goroutine to send the response to the stream
+	// goroutine to send the responses back to the client
 	grp.Go(func() error {
 		for {
-			var resp *v1.SourceTransformResponse
 			select {
 			case <-grpCtx.Done():
 				return grpCtx.Err()
-			case resp = <-senderCh:
-			}
-			if err := stream.Send(resp); err != nil {
-				return fmt.Errorf("failed to send response to client: %w", err)
+			case resp := <-senderCh:
+				if err := stream.Send(resp); err != nil {
+					return fmt.Errorf("failed to send response to client: %w", err)
+				}
 			}
 		}
 	})
 
+	var readErr error
 outer:
 	for {
-		// Stop reading new messages when we are shutting down
 		select {
-		case <-grpCtx.Done():
-			// If the context was cancelled while this loop is running, it will be caught and returned in one of the errgroup's goroutines.
+
+		case <-grpCtx.Done(): // Stop reading new messages when we are shutting down
 			break outer
 		default:
 		}
-
 		d, err := stream.Recv()
+		if err == io.EOF {
+			break outer
+		}
 		if err != nil {
-			if errors.Is(err, io.EOF) {
-				break
-			}
-			return err
+			log.Printf("Failed to receive request: %v", err)
+			readErr = err
+			// read loop is not part of the error group, so we need to cancel the context
+			// to signal the other goroutines to stop processing.
+			cancel()
+			break outer
 		}
-
-		req := d.Request
 		grp.Go(func() (err error) {
-			defer func() {
-				if r := recover(); r != nil {
-					log.Printf("Panic inside source transform handler: %v %v", r, string(debug.Stack()))
-					// We only listen for 1 message on the shutdown channel. If multiple requests panic, only the first one will succeed.
-					// The one that succeds returns the errTransformerPanic. This causes grpCtx to be cancelled.
-					select {
-					case fs.shutdownCh <- struct{}{}:
-					case <-grpCtx.Done():
-					}
-					err = errTransformerPanic
-				}
-			}()
-			var hd = NewHandlerDatum(req.GetValue(), req.EventTime.AsTime(), req.Watermark.AsTime(), req.Headers)
-			messageTs := fs.Transformer.Transform(grpCtx, req.GetKeys(), hd)
-			var results []*v1.SourceTransformResponse_Result
-			for _, m := range messageTs.Items() {
-				results = append(results, &v1.SourceTransformResponse_Result{
-					EventTime: timestamppb.New(m.EventTime()),
-					Keys:      m.Keys(),
-					Value:     m.Value(),
-					Tags:      m.Tags(),
-				})
-			}
-			resp := &v1.SourceTransformResponse{
-				Results: results,
-				Id:      req.GetId(),
-			}
-			select {
-			case senderCh <- resp:
-			case <-grpCtx.Done():
-				return grpCtx.Err()
-			}
-			return nil
+			return fs.handleRequest(grpCtx, d, senderCh)
 		})
 	}
 
+	// wait for all the goroutines to finish, if any of the goroutines return an error, wait will return that error immediately.
 	if err := grp.Wait(); err != nil {
+		fs.shutdownCh <- struct{}{}
 		statusErr := status.Errorf(codes.Internal, err.Error())
 		return statusErr
 	}
+
+	// check if there was an error while reading from the stream
+	if readErr != nil {
+		return status.Errorf(codes.Internal, readErr.Error())
+	}
+	return nil
+}
+
+// performHandshake handles the handshake logic at the start of the stream.
+func (fs *Service) performHandshake(stream v1.SourceTransform_SourceTransformFnServer) error {
+	req, err := stream.Recv()
+	if err != nil {
+		return status.Errorf(codes.Internal, "failed to receive handshake: %v", err)
+	}
+	if req.GetHandshake() == nil || !req.GetHandshake().GetSot() {
+		return status.Errorf(codes.InvalidArgument, "invalid handshake")
+	}
+	handshakeResponse := &v1.SourceTransformResponse{
+		Handshake: &v1.Handshake{
+			Sot: true,
+		},
+	}
+	if err := stream.Send(handshakeResponse); err != nil {
+		return fmt.Errorf("sending handshake response to client over gRPC stream: %w", err)
+	}
+	return nil
+}
+
+// handleRequest processes each request and sends the response to the response channel.
+func (fs *Service) handleRequest(ctx context.Context, req *v1.SourceTransformRequest, responseCh chan<- *v1.SourceTransformResponse) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			log.Printf("panic inside handler: %v %v", r, string(debug.Stack()))
+			err = errTransformerPanic
+		}
+	}()
+
+	request := req.GetRequest()
+	hd := NewHandlerDatum(request.GetValue(), request.GetEventTime().AsTime(), request.GetWatermark().AsTime(), request.GetHeaders())
+	messages := fs.Transformer.Transform(ctx, request.GetKeys(), hd)
+	var elements []*v1.SourceTransformResponse_Result
+	for _, m := range messages.Items() {
+		elements = append(elements, &v1.SourceTransformResponse_Result{
+			Keys:      m.Keys(),
+			Value:     m.Value(),
+			Tags:      m.Tags(),
+			EventTime: timestamppb.New(m.EventTime()),
+		})
+	}
+	resp := &v1.SourceTransformResponse{
+		Results: elements,
+		Id:      req.GetRequest().GetId(),
+	}
+	select {
+	case responseCh <- resp:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
 	return nil
 }