Convert RDS storage autoscaling events into a CloudWatch custom metric with EventBridge and Lambda for the dashboard

Why the Answer Is Correct

Amazon RDS emits storage autoscaling events to Amazon EventBridge. Creating an EventBridge rule that matches those events and targets an AWS Lambda function, where the function publishes a CloudWatch custom metric capturing the autoscaling activity, converts the event stream into a metric. That custom metric can then be rendered as a widget on a CloudWatch dashboard, which is what the requirement asks for. This is the standard event-to-metric pattern for surfacing RDS events on a dashboard.

Why the Other Options Are Wrong

B creates a CloudTrail trail for management events, sends them to CloudWatch Logs, and builds a metric filter for the autoscaling events. RDS storage autoscaling is not captured as a CloudTrail management event in a form this metric filter would match, so nothing would be charted. D does the same thing with data events instead of management events, which is even less applicable since data events cover S3 object-level and similar data-plane operations, not RDS autoscaling. C creates an EventBridge rule targeting a CloudWatch alarm so the alarm's status changes, but an EventBridge rule cannot target a CloudWatch alarm; there is no such integration, so this design does not function. A is the correct answer.

Community Comment Notes

Community voted A (85), with B a 15 percent minority. auxwww explicitly noted that autoscaling operations are not logged by AWS CloudTrail, which is the decisive objection to B and D. Shenannigan observed that both A and B would work only if the question had specified near real time and otherwise preferred B for simplicity, but trungtd and jamesf countered that the metric-filter approach via CloudTrail is indirect and complex compared with the EventBridge plus Lambda custom metric path.