====== CloudWatch Alarms ======

**What it is:** A rule that watches a metric and takes action when it crosses a threshold.

**What it’s for:**
  * Notify (SNS), scale (ASG), or trigger automation.
  * Detect outages or performance degradation early.

**Key ideas:**
  * Alarm states: OK, ALARM, INSUFFICIENT_DATA.
  * Alarms can be used for both ops alerts and auto scaling.

**Exam cues:**
  * “send notification when error rate is high” → alarm + SNS.
  * “trigger scale-out when CPU high” → alarm + ASG policy.

**Hard words:**
  * *notify* /ˈnoʊtɪfaɪ/: thông báo
  * *degradation* /ˌdeɡrəˈdeɪʃn/: suy giảm
  * *insufficient* /ˌɪnsəˈfɪʃnt/: không đủ