An application calculates its own pending-order count, and workers in an EC2 Auto Scaling group process the orders.
When the count exceeds a threshold, send an SNS notification and invoke an already configured scaling policy.
Which method is most appropriate?
Publish the application value with PutMetricData as a custom metric, then use a CloudWatch alarm for notification or scaling.
Detailed explanation
A dashboard displays existing measurements. Creating a widget does not publish values or configure actions.
A dashboard displays existing measurements. Creating a widget does not publish values or configure actions.
A custom metric represents the application count. Its metric alarm can notify SNS and invoke the configured scaling policy.
A custom metric represents the application count. Its metric alarm can notify SNS and invoke the configured scaling policy.
An SNS message does not create a CloudWatch time series or evaluate a numeric threshold.
An SNS message does not create a CloudWatch time series or evaluate a numeric threshold.
CPU usage is a different measurement and cannot directly test the required order count.
CPU usage is a different measurement and cannot directly test the required order count.
Check official documentation
Compare the following points with the official documentation.
Review PutMetricData series identity and metric-alarm notification/scaling actions.
Official references
What to confirm
Connect a published queue count to an alarm and explicit actions.
Key points
- PutMetricData
- Custom metric
- Queue length
Notes
- Environment: AWS SOA-C03 exam guide and the linked AWS documentation
- Reviewed against the linked AWS documentation on 2026-10-03.
Foundation review
Identify the custom series
Choose the namespace, metric name, dimensions, unit, timestamp, and value when publishing. The monitoring configuration must identify the intended series.
Measurement, evaluation, and action
Publishing does not itself notify or scale. Configure the metric alarm's threshold and evaluation periods, then attach SNS and EC2 Auto Scaling policy actions.