Make the future API support MessagePack
Msgpack is designed to fill the gap between efficient packed binary formats with a schema (Protobuf, Cap'n'Proto), and inefficient text formats without a schema (JSON, TOML, YAML). It functions as a drop-in replacement for JSON. The default for the API should probably be JSON but Msgpack could be activated with
Accept: application/msgpack, application/x-msgpack
Redis's builtin scripting functionality has native support for it, so if you happen to be using that (i.e. for caching rendered comment trees), Msgpack might come in handy.