Skip to main content

High Frequency Scaling Example

This example demonstrates an advanced deployment of Fast Autoscaler using AWS Step Functions to achieve high-frequency scaling checks (every 5-10 seconds instead of once per minute).

Why High Frequency?​

For workloads with rapid queue growth or stringent processing time requirements, the standard 1-minute CloudWatch Events trigger may not provide sufficient responsiveness. This approach, inspired by Zac Charles' article on triggering Lambda functions at sub-minute intervals, provides more frequent scaling decisions.

Architecture​

This approach uses:

  1. A Step Function state machine triggered every minute
  2. Within the state machine, a Map state with controlled concurrency
  3. Wait states that trigger the autoscaler Lambda at 10-second intervals

CloudFormation Template​

You can use the CloudFormation template in examples/high_frequency_step_function.yaml to deploy this solution.

Key components:

# Sample snippet - see full template in repository
AutoscalerStateMachine:
  Type: AWS::StepFunctions::StateMachine
  Properties:
    StateMachineType: EXPRESS
    RoleArn: !GetAtt StepFunctionRole.Arn
    DefinitionString: !Sub |
      {
        "Comment": "High-frequency autoscaler using Step Functions",
        "StartAt": "Initialize",
        "States": {
          "Initialize": {
            "Type": "Pass",
            "Result": {
              "index": 0,
              "checks": ${ChecksPerExecution},
              "timestamps": []
            },
            "Next": "CheckLoop"
          },
          # Additional states defined here

Performance and Cost Considerations​

This approach provides better responsiveness but comes with trade-offs:

  • Cost: Slightly higher due to Step Functions Express Workflow execution costs
  • Accuracy: Sub-minute scaling decisions with ~500ms precision
  • Complexity: More components to monitor and maintain

For most use cases, the standard deployment is sufficient. Consider this approach only for workloads with specific high-frequency scaling requirements.