Karpenter is an open-source Kubernetes node autoscaler created by AWS in 2021 and donated to CNCF in 2023, reaching v1.0 GA in November 2024. Unlike traditional node-group-based autoscalers, Karpenter watches for unschedulable pods and provisions right-sized nodes directly from cloud APIs, selecting the optimal instance type from hundreds of options simultaneously. Its consolidation feature continuously removes empty or underutilized nodes and repacks workloads onto fewer machines using three policies: WhenEmpty, WhenEmptyOrUnderutilized, and Balanced. Two core CRDs govern behavior: NodePool (scheduling constraints and disruption policy) and NodeClass (cloud infrastructure config). Karpenter is GA on AWS via EKS Auto Mode and on Azure AKS via Node Auto Provisioning, but has no official GKE provider as of mid-2026. Key limitations include inability to address over-requested pods, challenges with stateful workload eviction, and reactive-only Spot interruption handling.
