gRPC | XB Field Notes

The new message explicitly supplies count zero. A binary relay that does not know count retains its unknown explicit presence; a relay that knows count with implicit presence forwards the default zero without its presence. Both final values are zero, but only one remains explicitly supplied.

Protobuf evolution preserves meaning only within a defined contract

A gRPC rollout can leave old producers, new consumers, and intermediate services running together. Protobuf helps them exchange binary messages by identifying fields with numbers and wire types. That tolerance is narrower than application compatibility: a message can parse successfully while a consumer misunderstands its values, ignores a new instruction, or loses the distinction between absent and explicitly zero. ...

gRPC multiplexes many streams over one HTTP/2 connection

gRPC’s HTTP/2 transport lets multiple RPC attempts share a connection while keeping each stream’s messages ordered. That is useful for both short calls and long-lived exchanges. It does not make the connection an unlimited independent transport for every call: bandwidth, TCP delivery, connection flow control, and implementation resources remain shared. ...