Administrators/Optimize performance

Webserver

 * Use HHVM for highest performance
 * Use PHP 5.4 or later
 * Use APC for caching
 * Don't store the source code on NFS shares
 * Adapt PHP's realpath cache size
 * Serve static content from caches

Database

 * Several databases
 * Use read-only replicas

MySQL

 * Analyze and optimize cache tables regularly
 * Optimize MySQL server settings if necessary
 * Keep all indexes in memory
 * Load the most important indexes into the RAM

Cache

 * Use Redis to distribute the load
 * Fine-grained cache control