I've only done a little bit of this stuff, but so far my impression is your code will get more complicated in AWS if you glue in Flask/Sinatra/etc. for the API Gateway, but can still get a lot less complicated if you "think serverless" and run fairly tight functions in AWS Lambda. The system then takes care of auth, request parsing, response formatting, and most of the other stuff you'd do in Flask, plus of course it eliminates the actual web-server layer.
The downside is that you then need to call them via Lambda instead of using some kind of REST API -- however at least in my case, this turns out to be the much lesser evil as I'm only using them internally, and have my own code that makes the calls. My "lock in" is that I would have to change that code, but it's trivial.
The downside is that you then need to call them via Lambda instead of using some kind of REST API -- however at least in my case, this turns out to be the much lesser evil as I'm only using them internally, and have my own code that makes the calls. My "lock in" is that I would have to change that code, but it's trivial.