Facebook Chat looks very simple by design, but if you pry deeper you’ll learn that it’s an impressive engineering and design feat. One must question: how was Facebook Chat, which was to serve over 70 million users when it was built (now serving over 500 million), developed? Which programming language was used to build Facebook Chat? What technologies were put together to bake this web-based chat feature? The primary Facebook chat programming language is Erlang, but that was not the only ingredient. Much more has gone into developing Facebook chat.
At the heart of Facebook Chat, and thus the central part of this presentation, is a programming language called Erlang, which is a general-purpose concurrent, garbage-collected programming language and runtime system.