Karpenter Cluster Autoscaler Cheat Sheet

Updated 2026-05-22

Next Topic: KEDA Event-Driven Autoscaling Cheat Sheet

Karpenter is an open-source Kubernetes node autoscaler, originally developed by AWS and donated to the CNCF, that provisions and deprovisions EC2 nodes on demand by interacting directly with cloud provider APIs rather than through static node groups. Unlike the traditional Cluster Autoscaler, Karpenter takes a groupless, just-in-time approach: it watches for unschedulable pods, batches them, simulates scheduling requirements, and calls the EC2 Fleet API to launch precisely right-sized nodes within seconds. The key mental model is that Karpenter manages the full node lifecycle — provisioning, bin-packing, consolidation, drift, expiration, and interruption handling — using two CRDs: the provider-agnostic NodePool and the AWS-specific EC2NodeClass.

What This Cheat Sheet Covers

This topic spans 18 focused tables and 149 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Core Architecture and ComponentsTable 2: NodePool ConfigurationTable 3: EC2NodeClass ConfigurationTable 4: Just-in-Time Provisioning and BatchingTable 5: Consolidation and Bin-PackingTable 6: Spot Instance Integration and Interruption HandlingTable 7: Disruption Mechanisms — Expiration, Drift, and InterruptionTable 8: Scheduling Constraints and Pod PlacementTable 9: AMI and Node Image ManagementTable 10: GPU, Accelerator, and Multi-Architecture NodesTable 11: Capacity Reservations and Priority SelectionTable 12: IAM and Security SetupTable 13: Observability and MetricsTable 14: KEDA Integration for Event-Driven ScalingTable 15: Migration from Cluster AutoscalerTable 16: Feature Gates and Advanced FeaturesTable 17: Common Pitfalls and TroubleshootingTable 18: Multi-Cloud and Non-AWS Providers

Table 1: Core Architecture and Components

Karpenter's architecture separates provisioning policy from cloud-specific configuration into two CRDs, and uses a controller that watches Kubernetes API events to drive all node lifecycle decisions. Understanding the relationship between these components is the foundation for configuring and troubleshooting Karpenter effectively.

Component	Example	Description
NodePool	`apiVersion: karpenter.sh/v1` `kind: NodePool` `metadata:` `name: default` `spec:` `template:` `spec:` `nodeClassRef:` `group: karpenter.k8s.aws` `kind: EC2NodeClass` `name: default`	• Provider-agnostic CRD that defines scheduling constraints, capacity limits, disruption policy, and node expiration • every NodePool must reference an EC2NodeClass
EC2NodeClass	`apiVersion: karpenter.k8s.aws/v1` `kind: EC2NodeClass` `metadata:` `name: default` `spec:` `amiSelectorTerms:` `- alias: al2023@latest` `role: "KarpenterNodeRole-my-cluster"`	• AWS-specific CRD that defines AMI selection, subnets, security groups, IAM role, kubelet config, and user data • multiple NodePools can share one EC2NodeClass
NodeClaim	`apiVersion: karpenter.sh/v1` `kind: NodeClaim` `spec:` `requirements:` `- key: node.kubernetes.io/instance-type` `operator: In` `values: ["c5.large"]` `- key: karpenter.sh/capacity-type` `operator: In` `values: ["spot"]`	• Karpenter-internal CRD representing a single requested node • created automatically during provisioning and tracks the node from request through registration
Karpenter controller	`kubectl logs -n kube-system` `-l app.kubernetes.io/name=karpenter`	Kubernetes controller that watches unschedulable pods, runs scheduling simulations, creates NodeClaims, calls the EC2 Fleet API, and drives all disruption workflows.

Table 1: Core Architecture and Components

Component	Example	Description
NodePool	`apiVersion: karpenter.sh/v1` `kind: NodePool` `metadata:` `name: default` `spec:` `template:` `spec:` `nodeClassRef:` `group: karpenter.k8s.aws` `kind: EC2NodeClass` `name: default`	• Provider-agnostic CRD that defines scheduling constraints, capacity limits, disruption policy, and node expiration • every NodePool must reference an EC2NodeClass
EC2NodeClass	`apiVersion: karpenter.k8s.aws/v1` `kind: EC2NodeClass` `metadata:` `name: default` `spec:` `amiSelectorTerms:` `- alias: al2023@latest` `role: "KarpenterNodeRole-my-cluster"`	• AWS-specific CRD that defines AMI selection, subnets, security groups, IAM role, kubelet config, and user data • multiple NodePools can share one EC2NodeClass
NodeClaim	`apiVersion: karpenter.sh/v1` `kind: NodeClaim` `spec:` `requirements:` `- key: node.kubernetes.io/instance-type` `operator: In` `values: ["c5.large"]` `- key: karpenter.sh/capacity-type` `operator: In` `values: ["spot"]`	• Karpenter-internal CRD representing a single requested node • created automatically during provisioning and tracks the node from request through registration
Karpenter controller	`kubectl logs -n kube-system` `-l app.kubernetes.io/name=karpenter`	Kubernetes controller that watches unschedulable pods, runs scheduling simulations, creates NodeClaims, calls the EC2 Fleet API, and drives all disruption workflows.