Amazon EKS — KEDA — Event-Driven Scaling

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KEDA — Kubernetes Event-Driven Autoscaling

KEDA extends HPA to scale based on external events: SQS queue depth, Kafka lag, CloudWatch metrics, Prometheus queries, and 50+ other sources.

How KEDA Works

KEDA Architecture
┌──────────────────────────────────────────────────┐
│                                                  │
│  Event Source        KEDA           Kubernetes   │
│  ┌──────────┐    ┌──────────┐    ┌──────────┐  │
│  │ SQS      │───▶│ Scaler   │───▶│ HPA      │  │
│  │ Kafka    │    │          │    │ (pods)   │  │
│  │ CloudWatch│    │ ScaledObj│    │          │  │
│  │ Cron     │    │          │    │ 0→N pods │  │
│  └──────────┘    └──────────┘    └──────────┘  │
│                                                  │
│  Key feature: Can scale to ZERO (and back)       │
│  HPA alone can only scale to 1 minimum           │
└──────────────────────────────────────────────────┘

Install KEDA

$ helm repo add kedacore https://kedacore.github.io/charts
$ helm install keda kedacore/keda --namespace keda --create-namespace

Scale Based on SQS Queue

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: sqs-worker
spec:
  scaleTargetRef:
    name: worker-deployment
  minReplicaCount: 0     # Scale to zero!
  maxReplicaCount: 50
  triggers:
    - type: aws-sqs-queue
      metadata:
        queueURL: https://sqs.us-east-1.amazonaws.com/123456789012/my-queue
        queueLength: "5"    # 1 pod per 5 messages
        awsRegion: us-east-1
      authenticationRef:
        name: keda-aws-credentials

Common Scalers

Scaler Trigger Use Case
aws-sqs-queue Queue depth Worker processing
kafka Consumer lag Stream processing
prometheus Any Prometheus metric Custom metrics
cron Schedule Predictable traffic patterns
aws-cloudwatch Any CloudWatch metric AWS-native scaling

Common Mistakes

Mistake Impact
Not using IRSA for KEDA Can’t authenticate to AWS
Scale-to-zero without readiness check First request fails (cold start)
Too aggressive scaling Oscillation

What’s Next?

Practice: Auto Scaling Exercises.

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