When most people think of APIs, they think of a backend access point for client-server interactions in a distributed application. For many situations, this is indeed its purpose. But, an API can be much more than an interface between server-side logic and public consumers of that logic. For example, it is entirely possible to make it so that an API layer serves as the master control center for all activity taking place inside and outside a computing domain. In other words, an API layer can be the one ring that rules them all, which is the approach taken by Kubernetes.