DOP-C02 Exam Dumps : AWS Certified DevOps Engineer - Professional

The condition is deterministic: maximum CPU utilization must be below 2% for the previous 24 one-hour periods. That requires a static threshold, not anomaly detection. Anomaly detection learns a normal band from historical behavior, which is useful for unusual patterns but not for a fixed business definition of “idle.” CloudWatch alarms use “Datapoints to Alarm” as an M-out-of-N evaluation model, so 24 out of 24 means all 24 hourly datapoints must breach the threshold. AWS also documents idle-instance alarm examples based on CPU utilization staying below a threshold for 24 consecutive periods. Option D would alarm if only one hour was below 2%, which is far too sensitive. Options A and C use the wrong threshold type.

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The default CPU utilization metric does not reflect the processing backlog in the SQS queue, so the Auto Scaling group is not scaling properly to handle the workload.

To scale the Auto Scaling group based on queue length, you can create a target tracking scaling policy that uses a custom metric that combines the SQS queue ' s ApproximateNumberOfMessagesVisible and the number of instances (GroupIn-ServiceInstances) metric using CloudWatch metric math. This allows the scaling policy to calculate the average number of messages per instance and scale accordingly.

This approach requires no additional Lambda functions or log processing, thus minimizing operational overhead.

Option A and B require Lambda functions to publish custom metrics, which increases operational complexity. Option D also adds complexity with logging and metric filters.

The key requirement is to prevent non-approved EC2 instance types from being created at stack creation time , specifically when developers deploy AWS CloudFormation stacks. This is a pre-deployment enforcement requirement, not a detection or remediation requirement after resources already exist.

CloudFormation Guard Hooks are purpose-built for this use case. They allow organizations to define policy-as-code rules that validate CloudFormation templates before resources are created or updated. By writing a CloudFormation Guard rule that explicitly checks the InstanceType property against an approved allow list, the stack operation will fail immediately if a developer attempts to use a disallowed instance type. This enforces compliance early in the deployment lifecycle and avoids post-deployment cleanup.

Option B uses AWS Config, which only detects noncompliance after resources are created. Even with remediation, the instance would still be launched briefly, which violates the requirement. Option C uses an SCP, which applies broadly to all EC2 launches in the organization and is not limited to CloudFormation stacks; this is overly restrictive and could unintentionally block other valid use cases. Option A incorrectly combines Lambda with Guard Hooks—Guard Hooks natively evaluate Guard rules and do not invoke Lambda functions.

Therefore, using a CloudFormation Guard rule with a Guard Hook is the correct and AWS-recommended solution for enforcing approved EC2 instance types during CloudFormation deployments.