Design a public gRPC surface for external developers - the when-gRPC-at-all gate (most platforms keep gRPC internal and publish REST or transcoded JSON), AIP proto package and versioning conventions, buf breaking-change gates and their google.api.http blind spot, unary-by-default streaming decisions, the google.rpc.Status error model with its HTTP-mapping traps, transcoding and gateway architecture (Connect-RPC, grpc-gateway, Envoy), and external auth and TLS. Use whenever the user mentions gRPC
Define the versioning and deprecation policy for an API - version scheme choice (URI path, header, date-based account-pinned, or deliberate no-versioning), a written breaking-change definition, deprecation notice windows by audience, sunset communication (RFC 9745 Deprecation and RFC 8594 Sunset headers), enforcement at the sunset date (fall-forward vs hard cutoff), and breaking-change governance, with REST version-and-sunset and GraphQL continuous schema evolution treated as separate policies.
