I have a web-service that runs long-running jobs (in the order of several hours). I am developing this using Flask, Gunicorn, and nginx.
What I am thinking of doing
Celery and RQ is overengineering for simple task. Take a look at this docs - https://docs.python.org/3/library/concurrent.futures.html
Also check example, how to run long-running jobs in background for Flask app - https://stackoverflow.com/a/39008301/5569578