- How Facebook uses Erlang for real-time chat – Off the Grid!!
February 8, 2010 – This is a somewhat old blog post from a Facebook engineer describing how they engineered the chat system in Erlang. It’s notable because it contains a description of a scale testing technique I’ve never heard of before – they did a “dark launch” where real users pages were simulating status update connections and even fake message sending without ever drawing a single element on screen. This seems like a very novel way to get realistic load testing (realistic because it’s real people with real data) but without exposing your users to a system with bugs. Clever!