The Deployment API was introduced in Kubernetes version 1.2. It is replacing the replication controller. The functionalities of rolling-update and rollback by replication controller, it was achieved with client side (kubectl command and REST API), that kubectl need to keep connect while updating a replication controller. On the other hand, Deployments takes care of the process of rolling-update and rollback at the server side. Once that request is accepted, the client can disconnect immediately. 

Therefore, the Deployments API is designed as a higher-level API to manage ReplicaSet objects. This section will explore how to use the Deployments API to manage ReplicaSets.