For an application with the traffic and size of twitter, you're going to need at least three dedicated DBAs managing your MySQL installation (never have an even number of DBAs - it leads to tyranny), which is probably going to be spread out across a cluster of replicated servers. You're going to have a very beefy load balancer, behind which sits a bunch of nginx installs and you'll have likely thrown CI out the windo…
> never have an even number of DBAs - it leads to tyranny Please explain.
It's the same reason you never want an even number of supreme court justices. In the courts, it would lead to deadlock. In the server room, it will lead to bloodshed.