diff --git a/src/main/proto/grpc.proto b/src/main/proto/grpc.proto
new file mode 100644
index 0000000..eb5173f
--- /dev/null
+++ b/src/main/proto/grpc.proto
@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "com.loafle.overflow.db.api";
+
+message DBInput {
+    string targetDao = 1;
+    string method = 2;
+    map<string, string> params = 3;
+}
+
+message DBOutput {
+    string result = 1;
+}
+
+service DB {
+    rpc exec(DBInput) returns (DBOutput) {}
+}
+