We have added Memcached support to many sites we are hosting to speed up the page load. It is connected both to WordPress Object Caching and Mod_PageSpeed. The main difference with other caching mechanisms we use is that Memcached will store the cached assets in the server’s memory instead of the disk cache.
Since Memcached uses a lot of memory, it is enabled only on the websites receiving the most traffic.
Memcached is a distributed memory-caching system. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source (such as a database or API) must be read. Memcached is free and open-source software, licensed under the Revised BSD license.
Memcached is currently enabled on the following sites:
Basic principles of caching mechanism
In computing, a cache is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere. A cache hit occurs when the requested data can be found in a cache, while a cache miss occurs when it cannot. Cache hits are served by reading data from the cache, which is faster than recomputing a result or reading from a slower data store; thus, the more requests that can be served from the cache, the faster the system performs.