The Vertical Pod Autoscaler (VPA) is useful when you can’t create more copies of your Pods, but you still need to handle more traffic.

As an example, you can’t scale a database (easily) only by adding more Pods.

A database might require sharding or configuring read-only replicas.

But you can make a database handle more connections by increasing the memory and CPU available to it.

Lastly, the Cluster Autoscaler (CA).

When your cluster runs low on resources, the Cluster Autoscaler provision a new compute unit and adds it to the cluster.

If there are too many empty nodes, the cluster autoscaler will remove them to reduce costs.