diff --git a/ARCHITECTURE.md b/ARCHITECTURE.md
index 9669673ad3da7771a1118cd0b8a1e629139d5562..eb4d75df07fac1394707d87b25357fe08460084f 100644
--- a/ARCHITECTURE.md
+++ b/ARCHITECTURE.md
@@ -23,6 +23,8 @@ It also mentions **architecture invariants** and **API boundaries**
 
 API specification for gRPC and protobuf definitions.
 
+**Architecture invariant:** To import gRPC related protobuf definitions use `pb` as an import prefix. For gNMI related protobuf definitions use `gpb`
+
 ### `forks`
 
 Forks of `google/gnxi/gnmi` and `arista/goarista/gnmi` for gNMI server and client respectively. Subject of change once we converge to own clients and servers.