I always miss DJRF when using languages other than Python
You wouldn't need to think about promises or callbacks at first place, which would make things way easier. That's the main reason I gave up NodeJS for Go when working with APIs. Async programming is noise. CSP is a better paradigm.
[1]: http://doc.akka.io/docs/akka/2.4/general/actor-systems.html#...
Maybe the DRF for Ruby is grape https://github.com/ruby-grape/grape/blob/master/README.md but I never used it. I just fill in the standard scaffolded REST methods in the controllers with queries and write json views (Rails and Django have different terms and concepts, MVC vs MVT.)