Even if FaceBook and the BBC homepage (which I work on at the moment) was doing the same traffic (we are not, not even close), the work load wouldn’t even be in the same order of magnitude.
Now think what happens on Facebook. Let’s say you have 200 friends. When you hit your Facebook account it has to go gather the status of all 200 of your friends at the same time so you can see what’s new for them. That means 200 requests need to go out simultaneously, the replies need to be merged together, other services need to be contacted to get more details, and all this needs to be munged together and sent through PHP and a web server so you see your Facebook page in a reasonable amount of time. Oh my.
And
Their caching tier services 120 million queries every second and it’s the core of the site.
Ouch. Thats just insane.
