Caching

The last major subsystem that I will include here is the caching layer. Drupal 8 has gone to great lengths to improve the performance of building pages and rendering data. To this end, the caching system has become an important part to consider whenever we either do complex or heavy calculations or render content.

From a module developer's perspective, there are two main pillars of the caching system. The first one provides developers a cache backend to store the result of complex data calculations. This data can be read in the next requests to avoid the need for redoing those calculations. This goes hand in hand with cache invalidation when something in the system changes that would require the calculations to be redone. The second pillar is the render cache, which allows developers to wrap their data output with metadata that describe in what context and when that data output needs to be invalidated or changed. The entire markup of that bit gets cached and invalidated based on the rules of the metadata.

We will see these in action in a later chapter dedicated to caching.