[derefr]

Do you ever write "apps" that only expose an API, without rendering any HTML? I find Flask (or Ruby's Sinatra) to be ideal for that case.

Given hexagonal architecture (i.e. your model + business rules existing as a "service component" library project, that your webapp consumes as a dependency), if all you need is to expose that service with an API, Flask and/or Sinatra lets you do so with nothing more than a flat file of 3–6-line controller stanzas. It's really quite lovely; gets to the core of what it means for something to be a "microservice."

[akoumjian]

I suppose if you already have an existing service component that encapsulates authentication, authorization, business logic, notifications, and all that other jazz, then use flask is an excellent way to wrap that to produce an http api.