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The open-source autoscaler that picks the right nodes for Kubernetes, fast and cheap.
Quick Definition
Karpenter is an open-source Kubernetes cluster autoscaler that provisions right-sized nodes in response to pending pods. By rapidly launching and consolidating capacity, and favoring cost-effective or Spot instances, it improves both scheduling efficiency and Kubernetes cost optimization.
Karpenter is an open-source Kubernetes node autoscaler, created at AWS, that provisions exactly the machines pending workloads need. Where the classic cluster autoscaler grows pre-defined node groups of one fixed type, Karpenter looks at waiting pods and selects instance types, sizes, and purchase options on the fly from the provider's full catalog.
Its cost impact comes from three behaviors. It chooses cheaper instance shapes that still fit the pending pods, including spot capacity where workloads tolerate interruption. It launches nodes in seconds rather than minutes, so clusters can run leaner safely. And its consolidation feature continuously repacks workloads onto fewer, better-fitting nodes, then removes the empties.
Example. A platform team replaces twelve fixed node groups with Karpenter and a handful of provisioning rules. Consolidation alone shrinks the cluster by 28 percent in the first month, with no application changes and faster scale-ups during spikes.
Karpenter rewards good pod resource requests, since it sizes machines from them. Pair it with request rightsizing for the full effect. The Kubernetes Cost Management Guide covers node autoscaling strategy end-to-end.
Cluster autoscaler resizes fixed node groups. Karpenter picks instance types dynamically per workload, launches faster, and consolidates continuously.
It began on AWS and is most mature there, with support for other providers expanding through community implementations.
Yes, with correct pod disruption budgets. Karpenter respects them while moving workloads off underused nodes.