[toomim]

> Is there really any new-ish binary protocol these days?

HTTP/2 and HTTP/3 are binary protocols. And if you replace the JSON with CBOR, then even the payload becomes binary.

The reason for using HTTP is that the semantics are right. HTTP is a state transfer protocol, and ultimately, that's 90% of what you need for sync.

The other 10% is for subscriptions, updates, with versioning, and patches. You can get these by adding the Braid extensions (see braid.org) which upgrade HTTP from a state transfer to a state synchronization protocol. (I work on Braid.)