Why Kubernetes Cluster Autoscaler Loses to Karpenter After 6 Months in Production

Most teams adopt Cluster Autoscaler (CA) because it ships with EKS and works on day one. Six months later, they're staring at 12 node groups nobody fully owns, a cost report showing 30% idle capacity during off-peak hours, and a backlog of scaling incidents that hit during the morning traffic ramp.