grpc is lightweight, pretty fast, more universally supported than capn proto for other languages including javascript! and and gRPC's default transport is QUIC which is a UDP based replacement for TCP which aims at fixing "head of line" contention

if there is any candidate for an augmentation to nostr protocol it's gotta be grpc/protobuf

protobuf is the encoding, grpc is the protocol, it handles the request/response flow