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NodeOverlay with priceAdjustment shows volatile price #9222

@blankia

Description

@blankia

Description

Observed Behavior:
We are observing what appears to be significant price volatility in karpenter_cloudprovider_instance_type_offering_price_estimate when using a NodeOverlay with a price adjustment on a nodepool that is constrained to a specific Node Pool.

We would like to understand whether this behavior is expected or if this could indicate an issue in price estimation when combining NodeOverlays with NodePool-constrained spot capacity.

Interestingly, when applying the same overlay more broadly (for example, across the entire Availability Zone instead of limiting it to a specific NodePool), we no longer observe the same level of price volatility.

Image

Expected Behavior:
Observed price is somewhat stable / no huge volatility. Basically when NodeOverlay applied to AZ we see more stable prices compared to when applied to NodePool.

Reproduction Steps (Please include YAML):
Reproduction Steps (Please include YAML):
NodeOverlay Configuration:

apiVersion: karpenter.sh/v1alpha1
kind: NodeOverlay
metadata:
 creationTimestamp: "2026-05-27T09:21:02Z"
 generation: 1
 name: pricing-api-b-spot-overlay-8-aws
 resourceVersion: "3426395655"
 uid: 67274729-ef6d-4909-ae65-c2a89c318306
spec:
 priceAdjustment: -47%
 requirements:
 - key: karpenter.k8s.aws/instance-generation
  operator: In
  values:
  - "8"
 - key: karpenter.k8s.aws/instance-cpu-manufacturer
  operator: In
  values:
  - aws
 - key: karpenter.sh/nodepool
  operator: In
  values:
  - pricing-api-b-spot
status:
 conditions:
 - lastTransitionTime: "2026-05-27T09:23:21Z"
  message: ""
  observedGeneration: 1
  reason: ValidationSucceeded
  status: "True"
  type: ValidationSucceeded
 - lastTransitionTime: "2026-05-27T09:23:21Z"
  message: ""
  observedGeneration: 1
  reason: Ready
  status: "True"
  type: Ready

Versions:
Chart Version:
Karpenter 1.12.1
Kubernetes Version (kubectl version):
v1.35.4-eks-40737a8

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