Memcached is a general-purpose distributed memory caching system that is aimed at speeding up dynamic database-driven websites. It is used to reduce the number of times an external data source (like a database or API) is read by caching data and objects in RAM.
The Memcached system uses a client–server architecture. The server maintain a key–value associative array, while the clients populate this array and query it. Keys are up to 250 bytes long and values can be at most 1 megabyte in size.
The Memcached system is used by some of the most traffic heavy sites such as YouTube, Reddit, Facebook, Twitter. It is also supported by some popular CMSs such as Drupal, Joomla, and WordPress.
To use Memcached with PHP, go to PHP Configuration and enable memcached extension.