How to fix ScaleTargetRef not found in Kubernetes

Check if the deployment or workload referenced by the HPA actually exists:

kubectl get deployment <deployment-name> -n <namespace>
kubectl get replicaset <rs-name> -n <namespace>
kubectl get statefulset <sts-name> -n <namespace>

List all deployments in the namespace to find the correct name:

kubectl get deployments -n <namespace>

Note that names are case-sensitive.

View the current HPA configuration to identify mismatches:

kubectl get hpa <hpa-name> -n <namespace> -o yaml

Look at the scaleTargetRef section:

spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-deployment  # Must match exactly

Compare the name field with the actual deployment name.

HPA cannot target resources in other namespaces. Verify both are in the same namespace:

kubectl get hpa <hpa-name> -n <namespace>
kubectl get deployment <deployment-name> -n <namespace>

If they're in different namespaces, either:
1. Move the HPA to the same namespace as the target
2. Move the target to the same namespace as the HPA

Create the HPA in the correct namespace:

kubectl apply -f hpa.yaml -n <target-namespace>

For Kubernetes 1.16+, use apps/v1 for Deployments:

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1  # NOT extensions/v1beta1
    kind: Deployment
    name: my-deployment
  minReplicas: 1
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 80

The deprecated extensions/v1beta1 was removed in Kubernetes 1.16.

Ensure you're using the correct kind (Deployment, ReplicaSet, or StatefulSet):

# Check what type of resource you actually have
kubectl get all -n <namespace> | grep <name>

Common valid kinds for HPA:
- Deployment (most common)
- ReplicaSet
- StatefulSet

Note: You cannot target a Pod directly—only controllers that manage pods.

Update the HPA with the correct scaleTargetRef:

kubectl apply -f hpa.yaml -n <namespace>

Verify the HPA can now find and scale the target:

kubectl describe hpa <hpa-name> -n <namespace>

Look for:
- "AbleToScale: True" in conditions
- No "FailedGetScale" events
- TARGETS showing actual utilization percentages

kubectl get hpa <hpa-name> -n <namespace>