Cheat SheetsKubernetesScaling

Scaling — Cheat Sheet

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Cheat Sheet · AiCanCode.org
Scaling
Kubernetes1 topicsQuick revision reference
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Autoscaling — HPA, VPA & Cluster Autoscaler

Kubernetes has three autoscaling dimensions: HPA scales pod replicas based on CPU/memory/custom metrics, VPA adjusts pod resource requests, and Cluster Autoscaler adds/removes nodes based on pending pods.

  • ✓HPA scales pod count based on CPU/memory/custom metrics — requires Metrics Server.
  • ✓KEDA extends HPA to 50+ event sources (Kafka lag, SQS depth, Redis) and can scale to zero.
  • ✓Cluster Autoscaler adds nodes for Pending pods and removes underutilised nodes — reduces cloud cost.
  • ✓VPA recommends right-sized resource requests based on observed usage — start with updateMode: Off.
  • ✓Never run HPA and VPA in Auto mode on the same deployment — they conflict. VPA: Off mode + HPA is safe.
  • ✓Scale-to-zero with KEDA dramatically reduces costs for batch/event-driven workloads with idle periods.
hpa.yaml — HPA with CPU and custom metrics
# Prerequisite: install metrics-server

# kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml



# hpa.yaml — scale on CPU utilization

apiVersion: autoscaling/v2

kind: HorizontalPodAutoscaler

metadata:

  name: my-app-hpa

spec:

  scaleTargetRef:

    apiVersion: apps/v1

    kind: Deployment

    name: my-app

  minReplicas: 2

  maxReplicas: 20

  metrics:

    - type: Resource

      resource:

        name: cpu

        target:

          type: Utilization

          averageUtilization: 70    # target: keep avg CPU at 70%

    - type: Resource

      resource:

        name: memory

        target:

          type: AverageValue

          averageValue: 400Mi       # keep avg memory usage under 400Mi



# Scale on custom metric (Prometheus via prometheus-adapter)

    - type: External

      external:

        metric:

          name: http_requests_per_second

          selector:

            matchLabels:

              app: my-app

        target:

          type: AverageValue

          averageValue: "1000"      # 1000 req/s per pod



kubectl get hpa

# NAME         REFERENCE            TARGETS        MINPODS  MAXPODS  REPLICAS

# my-app-hpa   Deployment/my-app    45%/70%        2        20       3

#                                   ↑ current/target



kubectl describe hpa my-app-hpa    # see scale events and reasoning
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