Architecture
HPA scale to zero in Kubernetes 1.37: try it on k3s
Since Kubernetes 1.37 the HPA accepts minReplicas: 0 without enabling any feature gate, but only with an External or Object metric: CPU cannot do it, because with no pods there is no CPU to measure. On k3s 1.37 with a Redis queue and prometheus-adapter, the HPA requested the first pod after a median of 13 s and was back at 0 after 58 s.