I agree that if your server is just serving a JSON API, you're probably not using 90% of Django's capabilities. So you might as well use Flask instead. But as

I agree that if your server is just serving a JSON API, you're probably not using 90% of Django's capabilities. So you might as well use Flask instead. But as for non-relational databases or other external systems, Django does not help you nor hinder you in any way. If you want to connect to, say, Redis - the code would look the same under Django and under Flask. You simply don't use the ORM for those things, since it's irrelevant. You use the appropriate client library for connecting to the external system.