Cache API

In Drupal 11, the caching system is one of the most sophisticated parts of the architecture. It is designed to solve a specific problem: PHP is slow, but the database is even slower.
To understand the difference between the layers, it helps to look at them as a series of "gates." If a request can be answered at an early gate, Drupal doesn't have to do the heavy lifting of building the page.
1. The Hierarchy of Cache Layers
Drupal 11 uses a "layered" approach. When a user requests a page, Drupal checks these caches in order:
Layer A: Production/External Cache (Varnish/CDN)

• Read more about Precision Caching: A Systematic Guide to Troubleshooting Stale Assets in Drupal