This chapter dives into Drupal's code, taking a look at the underlying caching layer. It will begin with an accessible, high-level description before it dives into the actual implementation. Finally, it will teach module developers how to better use Drupal's built-in caching layers.

1. Understanding Drupal's Caching Layer
   1. Overview
   2. Variables
   3. The Many Cache Tables
2. Developing With Drupal's Caching Layer
   1. Drupal's Cache API
   2. Caching With Custom Modules
   3. Sessions