diff --git a/pkg/pb/data_service/data_service.pb.go b/pkg/pb/data_service/data_service.pb.go
index a61b1fe..abe760f 100644
--- a/pkg/pb/data_service/data_service.pb.go
+++ b/pkg/pb/data_service/data_service.pb.go
@@ -77,7 +77,8 @@ func (x *Identifier) GetSubject() string {
 type Message struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
 	Identifier    *Identifier            `protobuf:"bytes,1,opt,name=identifier,proto3" json:"identifier,omitempty"`
-	Payload       string                 `protobuf:"bytes,2,opt,name=payload,proto3" json:"payload,omitempty"` // JSON-encoded data
+	Payload       []byte                 `protobuf:"bytes,2,opt,name=payload,proto3" json:"payload,omitempty"`   // JSON-encoded data
+	Encoding      string                 `protobuf:"bytes,3,opt,name=encoding,proto3" json:"encoding,omitempty"` // e.g., "json", "protobuf"
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
@@ -119,10 +120,17 @@ func (x *Message) GetIdentifier() *Identifier {
 	return nil
 }
 
-func (x *Message) GetPayload() string {
+func (x *Message) GetPayload() []byte {
 	if x != nil {
 		return x.Payload
 	}
+	return nil
+}
+
+func (x *Message) GetEncoding() string {
+	if x != nil {
+		return x.Encoding
+	}
 	return ""
 }
 
@@ -428,12 +436,13 @@ const file_pkg_pb_data_service_data_service_proto_rawDesc = "" +
 	"\n" +
 	"Identifier\x12\x1a\n" +
 	"\bprovider\x18\x01 \x01(\tR\bprovider\x12\x18\n" +
-	"\asubject\x18\x02 \x01(\tR\asubject\"]\n" +
+	"\asubject\x18\x02 \x01(\tR\asubject\"y\n" +
 	"\aMessage\x128\n" +
 	"\n" +
 	"identifier\x18\x01 \x01(\v2\x18.data_service.IdentifierR\n" +
 	"identifier\x12\x18\n" +
-	"\apayload\x18\x02 \x01(\tR\apayload\"\x14\n" +
+	"\apayload\x18\x02 \x01(\fR\apayload\x12\x1a\n" +
+	"\bencoding\x18\x03 \x01(\tR\bencoding\"\x14\n" +
 	"\x12StartStreamRequest\"6\n" +
 	"\x13StartStreamResponse\x12\x1f\n" +
 	"\vstream_uuid\x18\x01 \x01(\tR\n" +
diff --git a/pkg/pb/data_service/data_service.proto b/pkg/pb/data_service/data_service.proto
index 44219e5..a6b2b0f 100644
--- a/pkg/pb/data_service/data_service.proto
+++ b/pkg/pb/data_service/data_service.proto
@@ -22,7 +22,8 @@ message Identifier {
 
 message Message {
   Identifier identifier = 1;
-  string payload = 2; // JSON-encoded data
+  bytes payload = 2; // JSON-encoded data
+  string encoding = 3; // e.g., "json", "protobuf"
 }
 
 // Control Requests and Responses
diff --git a/services/data_service/internal/domain/message.go b/services/data_service/internal/domain/message.go
index c211306..c73dd04 100644
--- a/services/data_service/internal/domain/message.go
+++ b/services/data_service/internal/domain/message.go
@@ -1,6 +1,14 @@
 package domain
 
+type Encoding string
+
+const (
+	EncodingJSON     Encoding = "json"
+	EncodingProtobuf Encoding = "protobuf"
+)
+
 type Message struct {
 	Identifier Identifier
-	Payload    any
+	Payload    []byte
+	Encoding   Encoding
 }
diff --git a/services/data_service/internal/provider/binance/futures_websocket.go b/services/data_service/internal/provider/binance/futures_websocket.go
index 3461e59..4a3faa7 100644
--- a/services/data_service/internal/provider/binance/futures_websocket.go
+++ b/services/data_service/internal/provider/binance/futures_websocket.go
@@ -141,7 +141,8 @@ func (b *FuturesWebsocket) readLoop() {
 				Provider: "binance_futures_websocket",
 				Subject:  container.Stream,
 			},
-			Payload: container.Data,
+			Payload:  []byte(container.Data),
+			Encoding: domain.EncodingJSON,
 		}
 
 		select {
diff --git a/services/data_service/internal/server/grpc_streaming_server.go b/services/data_service/internal/server/grpc_streaming_server.go
index 416606d..225e2a4 100644
--- a/services/data_service/internal/server/grpc_streaming_server.go
+++ b/services/data_service/internal/server/grpc_streaming_server.go
@@ -45,7 +45,8 @@ func (s *GRPCStreamingServer) ConnectStream(req *pb.ConnectStreamRequest, stream
 					Provider: msg.Identifier.Provider,
 					Subject:  msg.Identifier.Subject,
 				},
-				Payload: fmt.Sprintf("%v", msg.Payload),
+				Payload:  msg.Payload,
+				Encoding: string(msg.Encoding),
 			})
 
 			if err != nil {