When your application runs slow, throw some caches in. Well, at least it’s the easiest way to speed up things. What does a cache do? Say you have a function that takes some time to complete but the results would still be good enough if they were 5 minutes old. So then the idea is that you actually put the result of that calculation into a cache for some time.
Flask itself does not provide caching for you, but Flask-Caching, an extension for Flask does. Flask-Caching supports various backends, and it is even possible to develop your own caching backend.