It's worth pointing out that those servers are for the entire set of sites of which only SO is anywhere remotely close to capacity but yes there are three Web s

It's worth pointing out that those servers are for the entire set of sites of which only SO is anywhere remotely close to capacity but yes there are three Web servers for SO. And yes the hardware/bandwidth costs are (still) nothing. Read: http://highscalability.com/blog/2009/8/5/stack-overflow-architecture.html http://highscalability.com/blog/2009/8/5/stack-overflow-arch... (slightly outdated) and you'll see how cheap the servers are: single CPU, relatively low RAM. The 24 was a typo (now fixed). I updated the other too. Thanks for pointing that out.