Scalability refers to the ability to allocate and manage resources used by an application in order for the application to maintain an acceptable level of quality under a given workload. Most cloud offerings provide mechanisms for increasing the quality and quantity of resources used by an application. For example, the Azure App Service allows scaling of both the size of the App Service and the number of instances of the App Service.
Scalability can be viewed as demand on a limited number of resources. A resource could be disk space, RAM, bandwidth, or another aspect of software that can be quantified. The demand can range from the number of users, concurrent connections, or another demand that would produce a constraint on a resource. As the demand increases, a strain is placed on the application in order to provide the resource. When the strain affects the performance...
