Memcached

Memcached is an in-memory key/value cache store designed for distributed systems. Applications place frequently read data, such as query results or rendered fragments, in memory so they can skip slower backends. It is a long-established building block of web infrastructure and is released as open source under the BSD-3-Clause license.

The server is written in C, uses multiple threads and an event-based design built on libevent, and keeps its interface simple. Optional build features include TLS support through OpenSSL, process restrictions on Linux through libseccomp, and an experimental proxy mode. It can be compiled from a release tarball or from the git repository using the standard autotools workflow.

The project provides documentation on its website, including a tutorial, a wiki and a guide for diagnosing timeouts and odd behavior. Questions are handled through a mailing list rather than GitHub issues. Because it is a cache, operators typically run it on dedicated machines and avoid swapping when large memory is allocated.