lightbulbBook reference: Kleppmann, Designing Data-Intensive Applications, Ch. 4. Original notes kept below; rewrite them in your own words.
3.2.1 gRPC
You define a .proto service. Codegen produces clients and servers. HTTP/2 multiplexes streams.
Why it matters
JSON REST is chatty for internal fan-out. gRPC is smaller and has deadlines and streaming built in.
How it is used
Keep gRPC inside the mesh. Expose REST/JSON at the edge if browsers must call you (or use grpc-web). Version protobuf carefully.