I'm not sure how to answer your question regarding whether Vapor is viable for indie hackers, because I've only been skimming the docs and looking at small examples. But it seems to draw a lot of inspiration from Express.js and/or Ruby's Sinatra library. It doesn't seem to have the up-front complexity of something like Java's Spring Framework, although I understand you can use services and dependency injection if needed. So my first impression is it's easy to get started, but it enables you to refactor to something more complex if your application demands it.
