What it is: A service to collect, store, and search log data from AWS resources and applications.

What it’s for:

• Centralize application/system logs.
• Search logs to debug incidents.
• Set metric filters and alerts from logs.

Key ideas:

• Logs are stored in log groups and log streams.
• You can set retention to control cost.
• Integrates with Lambda and other services for automation.

Exam cues:

• “store EC2 app logs centrally” → CloudWatch Logs (via agent).
• “alert based on error pattern in logs” → metric filter + alarm.

Hard words:

• *centralize* /ˈsentrəˌlaɪz/: tập trung hóa
• *retention* /rɪˈtenʃn/: thời gian lưu giữ
• *pattern* /ˈpætərn/: mẫu (chuỗi lỗi)