AWS Certified CloudOps Engineer Associate SOA-C03 Practice Question

An operations team already has two CloudWatch metric alarms that go to ALARM when an Auto Scaling group's average CPUUtilization or MemoryUtilization exceeds predefined thresholds. The team now wants to receive a single SNS notification only when both metrics are breaching at the same time, while avoiding any additional CloudWatch charges for evaluating new metrics or sending duplicate notifications. Which solution meets these requirements?

Add a second SNS topic; subscribe each metric alarm to a different topic and use SNS message filtering so a notification is sent only when both topics receive messages.
Configure an EventBridge rule that listens for state-change events from both alarms within the same minute and forwards them to the SNS topic.
Create a CloudWatch composite alarm that uses an AND rule referencing the two existing metric alarms and configure the SNS action on the composite alarm only.
Create a metric math expression that multiplies the two metrics, configure a new metric alarm on that expression, and attach the SNS action to the new alarm.

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Answer Description

A composite alarm can reference the two existing metric alarms in an AND expression. The composite alarm itself does not evaluate any additional metrics, so it does not add CloudWatch charges. By attaching the SNS action only to the composite alarm, the team receives exactly one notification when both underlying alarms are in ALARM, eliminating duplicate messages.

A metric-math alarm would require creating and evaluating a new expression, and it still triggers independently of the original alarms. An EventBridge rule would need two separate events and could still send duplicates if timing differs. Subscribing multiple topics or using SNS message filtering cannot guarantee a single notification that depends on both alarms being ALARM simultaneously.

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