Imagine you’re the founder of a brand-new video streaming service. You have a handful of users at first, but after a celebrity endorsement, demand explodes to ten million users overnight. Twenty years ago, you’d need to buy racks of servers, spend weeks installing them, and probably crash under the load anyway. Today, you can handle that surge by simply renting computing power by the hour, scaling up and down automatically. This is the promise of cloud computing and the modern IT models that make it possible.