Flask-Limiter adds rate limiting to Flask applications.

By adding the extension to your flask application, you can configure various rate limits at different levels (e.g. application wide, per Blueprint, routes, resource etc).

Flask-Limiter can be configured to persist the rate limit state to many commonly used storage backends via the limits library.

Source: https://flask-limiter.readthedocs.io/en/stable/

A Blueprint is a way to organize a group of related views and other code.
Rather than registering views and other code directly with an application, they are registered with a blueprint.
Then the blueprint is registered with the application when it is available in the factory function.