[budu3]

- We've built a lightweight but powerful multi-language RPC framework that allows us to seamlessly and easily tie together subsystems written in any language, running on any platform. Facebook is built in PHP, C++, Perl, Python, Java, and even a little bit of ML—and it all works together.

- We are the largest user in the world of memcached, an open-source caching system. Originally developed by LiveJournal, we've since made so many scalability improvements and performance upgrades that we will be the primary contributor of features in the next major release.

- We've created a custom-built search engine serving millions of queries a day, completely distributed and entirely in-memory, with real-time updates.

http://www.facebook.com/jobs_engineering.php