It was never meant to handle real traffic, the goofy ajax loader 99 times out of a hundred fails to load any content, sure they are growing fast but they should just turn that shit off and cache the main pages, people would rather read content than get up to the second like/comment counts.

Without knowing how much hardware/cpu they need to run the traffic they have it is hard to know but I am sure that with some smart use of cache, redis, and a db designed for tens of millions of requests per day the site would not be the steaming pile of dogshit it is now