In Zeebe, when does it use grpc and when does it use pub/sub bus to communicate
Hi @shashi, Zeebe uses gRPC to communicate between your code (workers) and the broker cluster.
Internally, Zeebe uses a hyper-efficient SBE binary protocol to communicate between the brokers and the gRPC gateway, and uses pub/sub for message delivery - but these are internal implementation details of Zeebe and are not exposed to your application architecture.
Actually, to clarify this: you can publish messages to running workflows instances. These are published over gRPC from your client code, and correlated with the appropriate instance on the broker. See here.