The libevent library is probably best known by its use in memcached . memcached is one of the key components of the LAMP stack. However the recent trend seems to instead highlight NoSQL solutions where typical RDBMS and memcached are replaced with more optimized and dedicated systems. The importance of libevent is not affected at all by that trend since it's not tied to any applications and can be used for NoSQL solutions. Tor is another use case of libevent. libevent is crucial for its cross-platform availability. One of the developers of libevent is Nick Mathewson who is also the key person behind the Tor project. My interest in libevent stems from my own project, the DICE . From the beginning of the development in 2002, its I/O is fully optimized to Windows and I/O Completion Ports (IOCP) without using any middleware or libraries. Even though it works flawlessly in its current state, replacing it with a decent OSS library can be a good chance to make it more robust and fut