perf(server): batch achievement updates and eliminate redundant snapshots, writes and JSON round trips

go/internal/server/protocol/protocol.go

@@ -31,15 +31,25 @@ func Encode(code int, proto, key []byte, now int64) ([]byte, error) {
 // Notify is plain base64 protobuf in the JSON envelope. The client parses it
 // separately after decrypting the response data (NetworkManager.OnAfterResponse).
 func EncodeWithNotify(code int, proto, key []byte, now int64, notify []byte) ([]byte, error) {
-	data, err := cryptox.EncryptBase64Payload(proto, key)
+	envelope, err := EnvelopeWithNotify(code, proto, key, now, notify)
 	if err != nil {
 		return nil, err
 	}
-	return json.Marshal(Envelope{
+	return json.Marshal(envelope)
+}
+
+// EnvelopeWithNotify builds the same wire response without an intermediate
+// JSON round trip when the caller is assembling a batch.
+func EnvelopeWithNotify(code int, proto, key []byte, now int64, notify []byte) (Envelope, error) {
+	data, err := cryptox.EncryptBase64Payload(proto, key)
+	if err != nil {
+		return Envelope{}, err
+	}
+	return Envelope{
 		PacketCode: code, Length: base64.StdEncoding.EncodedLen(len(proto)),
 		Data: data, ServerNowTime: now,
 		Notify: base64.StdEncoding.EncodeToString(notify),
-	})
+	}, nil
 }
 
 type BatchRequest struct {