Espresso is all about speed. That's why it was invented by an Italian factory owner -- to reduce the time his employees spent on coffee break by producing a shot that was both quick-to-brew and drink. It's also the key to a shot's quality. To little time, and the result is a watery and under-extracted brew -- caused by a too-course grind. Too long, and the opposite problems occur -- of course, the cause is opposite too. The experts disagree on an exact sweet spot, but generally speaking, it should take ~25 seconds to pull an optimal shot, complete with a rich caramely crema. Just about as long as it takes you to read this post.