Investigate FastAPI and possibly switch from Flask to FastAPI

[fgypas]

Is your feature request related to a problem? Please describe.
It seems that FastAPI is much more efficient than Flask and has some great features.

Describe the solution you'd like
I think it would be great if we (first) investigate and (later) switch the back-end from Flask to FastAPI

[fgypas]

@vsoch Do you have any experience with FastAPI (in comparison to Django or Flask)?

[vsoch]

I've heard of FastAPI and have seen how it can be used alongside, but my preference is for using fewer dependencies, and also more stable (less new) things, so I haven't had the incentive to use it. I would want to see evidence that a Flask or Django API is not sufficiently fast for a use case before deciding it's needed.