An application that is running on a web server can only process requests that can fit the computing resources that the server contains. As more requests are sent to the application, resources begin to decrease, and at some point, new requests will start to fail and our customer will start experiencing a degradation of service and performance.

The ability of your service to handle increasing amounts of requests is called Scalability, and there are two ways in which your service can scale: Scale Up and Scale Out.