The Authcache module offers page caching for both anonymous users and logged-in authenticated users. This allows Drupal/PHP to only spend 1-2 milliseconds serving pages, greatly reducing server resources.
On 404 Not Found error pages, Drupal will skip rendering of several pieces of your website for performance reasons.
Pressflow is a derivative of Drupal core providing enhanced performance, scalability, and data integrity. Pressflow addresses a long-standing problem: High-traffic sites use stable versions of Drupal, and stable versions of Drupal are ineligible for enhancements to solve performance bottlenecks discovered after widespread deployment.
