Autoscale is a built-in feature of Cloud Services, Mobile Services, Virtual Machines, and Websites that helps applications perform their best when demand changes. Of course, performance means different things for different applications. Some apps are CPU-bound, others memory-bound. For example, you could have a web app that handles millions of requests during the day and none at night. Autoscale can scale your service by any of these—or by a custom metric you define.