A long-awaited Karpenter feature is finally here!

The latest Karpenter release supports Capacity Buffer, eliminating the need for workarounds such as balloon pods to maintain spare node capacity.

A Capacity Buffer defines virtual placeholder pods that exist only in Karpenter’s scheduling simulation — they are never created as actual Kubernetes pods.

These virtual pods tell Karpenter to provision nodes with spare capacity. They participate in each scheduling cycle to maintain the buffer and are automatically refilled as real workloads consume the pre-provisioned capacity.

Benefits over previous workarounds:

• No balloon pods: Eliminates the need for low-priority placeholder deployments and complex PriorityClass configurations.

• More efficient scaling: Capacity can be defined using fixed counts or percentages, allowing spare capacity to scale with your workload instead of over-provisioning entire node pools.

• Automatic replenishment: The buffer is automatically maintained as workloads consume the available capacity.

A much cleaner approach to keeping capacity readily available without relying on Kubernetes scheduling hacks.

• 1.14.0 Github release: https://github.com/kubernetes-sigs/karpenter/releases/tag/v1.14.0
• Documentation: https://karpenter.sh/docs/concepts/capacitybuffers/
• The outdated baloon pod trick: https://kubernetes.io/docs/tasks/administer-cluster/node-overprovisioning/

balloon deployment
Buffer api in progress:
https://github.com/kubernetes-sigs/karpenter/issues/2571
https://github.com/kubernetes/autoscaler/pull/8151

Old proposal: pod headroom