Ask HN: What is the fastest way to build an api for mobile back end?

If you were going to build a consumer mobile app as fast as possible, as a one-man or one-woman dev team, what technologies and tools would you use to build out the server side? Say you have 1 week to put together an MVP.

One answer is that one should use the technologies he/she is most familiar with, but what would you recommend to skilled engineers who are most experienced with client development?

Specifically, are there tools that significantly speed up the api development process, e.g. scaffolding tools, or stuff like Amazon API Gateway + Lambda?