[davedunkin]

As of 2016, Stack Overflow ran on dozens of servers in two data centers.

https://nickcraver.com/blog/2016/03/29/stack-overflow-the-ha...

[mehrdadn]

Also interesting what their minimum requirements were in 2014 :https://nickcraver.com/blog/2013/11/22/what-it-takes-to-run-...