Loading...
The open-source autoscaler that picks the right nodes for Kubernetes, fast and cheap.
Quick Definition
Karpenter is an open-source Kubernetes node autoscaler, originally built by AWS and now a CNCF project, that provisions right-sized nodes in direct response to pending pods. Instead of scaling fixed node groups, it reads the pods waiting to be scheduled and launches the specific instance types, sizes, and purchase options that fit them, then consolidates workloads onto fewer nodes as demand falls. It typically improves both scheduling speed and Kubernetes cost efficiency.
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 adds and removes nodes within pre-defined node groups of a fixed instance type, so your choices are set in advance. Karpenter has no node groups: it reads pending pods and selects instance types, sizes, and purchase options dynamically from the provider's full catalog. It also launches nodes in seconds rather than minutes and continuously consolidates workloads onto fewer nodes, which cluster autoscaler does not do.
Karpenter began at AWS and remains most mature there, where it supports the full EC2 instance catalog including Spot capacity. It is now a CNCF project with a provider-agnostic core, and community implementations extend it to other clouds, though feature parity varies. For non-AWS clusters, check the maturity of the specific provider implementation before relying on it in production.
Yes, when pod disruption budgets are configured correctly. Consolidation moves workloads off underused nodes and terminates the empties, and Karpenter respects disruption budgets and node termination grace periods while doing so. The usual failure mode is not Karpenter itself but missing or overly permissive disruption budgets, so set those before enabling consolidation.
Yes. Karpenter is open-source software released under the Apache 2.0 licence and there is no licence fee. You pay only for the cloud infrastructure it provisions, which is usually less than you paid before, since it selects cheaper instance shapes and consolidates unused capacity.
Savings depend on how over-provisioned the cluster was to begin with. Teams replacing fixed node groups commonly see cluster costs fall by 20 to 30 percent from consolidation and better instance selection alone, with more available when Spot capacity is used for interruptible workloads. The gains are largest where pod resource requests are accurate, since Karpenter sizes nodes from them.