Eugene Letuchy (a Facebook Engineer) talks about Facebook Chat

"One of the things I like most about working at Facebook is the ability to launch products that are (almost) immediately used by millions of people. Unlike a three-guys-in-a-garage startup, we don't have the luxury of scaling out infrastructure to keep pace with user growth; when your feature's userbase will go from 0 to 70 million practically overnight, scalability has to be baked in from the start. The project I'm currently working on, Facebook Chat, offered a nice set of software engineering challenges:"

• Real-time presence notification
• Real-time messaging
• Distribution, Isolation, and Failover
• Glueing with Thrift

Here is the original post by Eugine
http://www.facebook.com/note.php?note_id=14218138919

Ever wondered how Gmail/Facebook chat works?

Web based IM clients are seem to be the flavour of the month at the moment. Gmail has had one for a little while now and more recently Facebook has added this to their already impressive stable of features. These are really cool, and rip all over the old form based chat rooms, but how do they do it without using any plugins, flash or the dreaded ActiveX componets?

Interested in finding details? k. Here where to find more...
http://technophiliac.wordpress.com/2008/05/28/ever-wondered-how-gmailfacebook-chat-works/