Although scaling pods on CPU and memory usages is quite intuitive, sometimes it's inadequate to cover situations such as scaling with network connections, disk IOPS, and database transactions. As a consequence, the custom metrics API and external metrics API were introduced for Kubernetes components to access metrics that aren't supported. We've mentioned that, aside from Resource, there are still Pods, Object, and External type metrics in an HPA.
The Pods and Object metrics refer to metrics that are produced by objects inside Kubernetes. When an HPA queries a metric, the related metadata such as the pod name, namespaces, and labels are sent to the custom metrics API. On the other hand, External metrics refer ...
