Lesson 21 / 26

CloudWatch Alarms at a Glance

Turning a bad metric into an automatic notification or action.

What an alarm is

A CloudWatch alarm watches one metric and triggers when it crosses a threshold — e.g. CPU above 80% for 5 minutes — moving you from checking dashboards to being notified.

Alarms can act, not just alert

An alarm can send a notification (via SNS to email/Slack) or trigger an action directly, like scaling out an Auto Scaling Group when load is high.

Set alarms before you need them

Add alarms for CPU, error rates, and queue depth on day one — finding out about an outage from a customer instead of an alarm is a bad first sign.

Quick check: What can a CloudWatch alarm do besides sending a notification?

  • Nothing, it only notifies
  • Trigger an action, like Auto Scaling
  • Automatically fix application bugs
Answer

Trigger an action, like Auto Scaling — Alarms can trigger Auto Scaling actions or other automated responses, not just notify.