# The Scale Cube Is a method for classifying different methods of [[Application Scaling]]. It was introduced in a book called *The Art of Scalability* by Martin L. Abbott and Michael T. Fisher. ## X-Axis Scaling Also known as horizontal scaling, is the most common method. Multiple application instances run behind a load balancer of some sort. ## Y-Axis Scaling Also known as vertical scaling, is an application scaling method in which different parts of the application are split-off and ran on different hardware. Aside form performance benefits this improves development scalability as well. If separate application parts are granular, this corresponds to a [[Microservice Architecture]]. ## Z-Axis Scaling Multiple application instances run at the same time and each instance is responsible for a subset of the data. Some router service must exist to route requests to the appropriate application instance. This kind of scaling is often used to scale databases.