[rest] REST vs JSON-RPC?

If your service works fine with only models and the GET/POST/PUT/DELETE pattern, use pure REST.

I agree that HTTP is originally designed for stateless applications.

But for modern, more complex (!) real-time (web) applications where you will want to use Websockets (which often imply statefulness), why not use both? JSON-RPC over Websockets is very light so you have the following benefits:

  • Instant updates on every client (define your own server-to-client RPC call for updating the models)
  • Easy to add complexity (try to make an Etherpad clone with only REST)
  • If you do it right (add RPC only as an extra for real-time), most is still usable with only REST (except if the main feature is a chat or something)

As you are only designing the server side API, start with defining REST models and later add JSON-RPC support as needed, keeping the number of RPC calls to a minimum.

(and sorry for parentheses overuse)