In the previous chapter, we explored some of the core concepts for application updates using the old rolling-update method. Starting with version 1.2, Kubernetes added the Deployment construct, which improves on the basic mechanisms of rolling-update and ReplicationControllers. As the name suggests, it gives us finer control over the code deployment itself. Deployments allow us to pause and resume application rollouts via declarative definitions and updates to pods and ReplicaSets. Additionally, they keep a history of past deployments and allow the user to easily roll back to previous versions.
Note
It is no longer recommended to use ReplicationControllers. Instead, use a Deployment that configures a ReplicaSet in order to set up application availability for your stateless services or applications. Furthermore, do not directly manage the ReplicaSets that are created by your deployments; only do so through the Deployment API.