A CloudWatch alarm watches a metric and takes an action when it crosses a threshold — sending an SNS notification, triggering Auto Scaling, or recovering an instance.
What alarms can trigger
Alarms commonly notify a team via SNS, drive Auto Scaling policies, or trigger EC2 auto-recovery. They have states (OK, ALARM, INSUFFICIENT_DATA) and can require a metric to breach for several periods before firing. The tell is “take an automated action when a metric crosses a threshold.”
Test yourself
You want to automatically notify the on-call team and add capacity when CPU across a fleet stays high. What ties the metric to those actions?
- AWS Config rules
- A CloudWatch alarm (with SNS and Auto Scaling actions)
- CloudTrail
- A NAT gateway
👉 Click to reveal the answer & explanation
Correct answer: B. A CloudWatch alarm watches the metric and triggers actions like an SNS notification and an Auto Scaling policy when the threshold is breached. Config (A) checks configuration; CloudTrail (C) logs API activity; NAT (D) is networking.
Related topics
Amazon CloudWatch · Auto Scaling · Amazon SNS
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