just speaking from experience here, i have done a lot of custom codecs and custom RPC APIs and i don't do them anymore... i used my experience to improve the way that fiatjaf's golang library for nostr is written and architected, but i would not write my own codecs now so readily or at least use tools that make it a lower debug time and easier maintenance thing, and actually, if i could avoid it, i'd not rewrite the RPC API framework and codec, and just use grpc/protobuf

i have a very nice guide on how to do grpc/protobuf apps in golang https://github.com/quanterall/kitchensink