Facebook Chat

Found at Yariv's Blog: Facebook Chat is an article about the technology behind the Facebook social network.

They have a large web application with up to 70 Million users and want to provide them with presence information (like: "I am online", "I am busy", "I am away", "I am offline").

As the bidirectional information channel between the user's web browser and the Facebook servers they use BOSH, the XMPP way of binding XMPP via HTTP requests. The requests for BOSH are handled by a web server implemented in Erlang.