You can read on various massively scalable webapps architecture. http://highscalability.com/ http://highscalability.com/ seems to aggregate those, and you can f

You can read on various massively scalable webapps architecture. http://highscalability.com/ http://highscalability.com/ seems to aggregate those, and you can find articles and slides published by the developers of more services if you do some googling. The key to speed and load tolerance is massive multilevel caching; every service does caching differently but they all do.