Is autoscaling in RDS Aurora a built-in feature or does it need to be enabled manually during deployment?

Auto-scaling storage in RDS Aurora is a core feature. When creating an Aurora cluster, Storage Auto Scaling is enabled by default and automatically increases storage size as data grows, up to a maximum size of 128TiB.

Auto Scaling for Aurora Replicas can also be enabled during or after deployment for automatic addition and removal of Aurora replicas depending on the load on the primary instance. This is not a core feature and must be explicitly configured.

Configuring replica auto-scaling via AWS CLI:

# Enable Auto Scaling for replicas
aws rds put-scaling-policy \
  --resource-id cluster:<your-cluster-identifier> \
  --policy-name aurora-replica-autoscaling-policy \
  --policy-document='{
    "AutoScalingTargetTrackingScalingPolicyConfiguration": {
      "TargetValue": 25.0, // Target CPU utilization percentage
      "ScaleOutCooldown": 300, // Cooldown period after scaling out (seconds)
      "ScaleInCooldown": 300, // Cooldown period after scaling in (seconds)
      "PredefinedMetricSpecification": {
        "PredefinedMetricType": "RDSReaderAverageCPUUtilization"
      }
    }
  }' \
  --scalable-dimension rds:cluster:ReadReplicaCount \
  --min-capacity 1 // Minimum number of replicas
  --max-capacity 10 // Maximum number of replicas