What programing languages are used to make Facebook?

[Mr Answer]

The frontend is written in PHP (programming language). Much of it is written using XHP, and the runtime is HipHop for PHP. Like most websites there's a lot of JavaScript (programming language) running in the users' browsers.

Most of the backend services are written in C (programming language), C++ and Java. A lot of the C++ services rely on Boost. Many of the internal tools and some glue code is written in Python (programming language). One of the services that underlies Chat, the channel servers (see http://www.facebook.com/note.php... ), is written in
Erlang. The backend services and the web frontend communicate using Apache Thrift. The iPhone app and iOS SDK are written in Objective-C (programming language).

OCaml, Haskell, and Ruby (programming language) are used internally, but as far as I know they don't power anything available on the website.