In a traditional REST API, where do non-RESTful things (like other API calls, or "business logic") tend to go?
Is there /db/restEndpoints and /rpc/nonRESTfulEndpoints?
Is there /db/restEndpoints and /rpc/nonRESTfulEndpoints?
Other API calls depend on the purpose. If its part of the business logic, it's probably back end and hidden as described above.
If the other API call simply powers the UI, you might keep it in the client. One example is autocomple for facebook friends. The client can call facebook for a list, let the user select their friend, and then send that friends info to your API.
With that said, I'm not sure how either of those are "non-RESTful" so maybe I missed the point of the question?