Three autoscalers, three genuinely different dimensions.
Confusing them is a common source of "why isn't this scaling" confusion.
MechanismScalesAvailable on
HPAPod replica countBoth
VPAPer-pod CPU/memory requestsBoth
Cluster AutoscalerNode countStandard only
A node pool is Standard mode's own equivalent of a managed instance group — its own machine type, autoscaling range, and upgrade policy, independent of other pools.