When using gRPC in production, at some point the following problems become more appearant:
It's hard to break protobuf schemas, but possible. Check out how to absolutely prevent it: Schema Breaking changes
gRPC connections are HTTP2 based - meaning multiple requests are multiplexed on each connection.
A client will have all of his requests sent on the first connection it opened. Check out an awesome way to solve this, and also benefit from a variety of additional tools and capabilities: LinkerD