TL;DR

Kubernetes' built-in Horizontal Pod Autoscaler (HPA) only scales on CPU/memory and cannot go below 1 replica — so it can neither react to event sources (queue depth, HTTP backlog) nor ever scale to zero. KEDA (Kubernetes Event-Driven Autosc…

How it works

The built-in HPA is the only autoscaler most teams reach for, and it has two hard limits baked in:

Key takeaways