<p>As the title suggests, I can't find any difference between Prometheus Adapter and Prometheus Operator for monitoring in Kubernetes.</p>
<p>Can anyone tell me the difference? Or if there are particular use cases in which to use one or the other?</p>
<p>Thanks in advance.</p>

Humbrum
<p>Those are completely different things. Prometheus Operator is a tool created by CoreOS to simplify deployment and management of Prometheus instances in K8s. Using Prometheus Operator you can very easily deploy Prometheus, Alertmanager, Prometheus alert rules and Service Monitors.</p>

<p>Prometheus Adapter is required for using Custom Metrics API in K8s. It is used primarily for Horizontal Pod Autoscaler to scale based on metrics retrieved from Prometheus. For example, you can create metrics inside of your application and collect them using Prometheus and then you can scale based on those metrics which is really good, because by default K8s is able to scale based only on raw metrics of CPU and memory usage which is not suitable in many cases.</p>

<p>So actually those two things can nicely complement each other.</p>
