In a post on the Twitter Engineering Blog yesterday, Twitter revealed that they receiver over 1,000 tweets per second and 12,000 queries per second, equalling over 1 billion queries per day!

This announcement comes with the upgrade of their backend system over the past few weeks. Expecting this software to last for a number of years, Twitter is currently only using 5% of its resources, and can index "roughly 50 times more Tweets per second" than they currently do.