Amazon CloudWatch
CloudWatch is the observability layer that gathers metrics, logs, and alarms from AWS resources and applications into one place. It turns current system state into numbers and events, then connects notifications or automated actions when thresholds are crossed.
▶Architecture Diagram
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If error rates rise after a deployment and you have to open EC2 logs, Lambda logs, and queue backlog separately, root-cause analysis slows down immediately. When metrics and alarms are not gathered in one place, incidents become obvious only after they have already grown.
In the past, each server had its own log files and monitoring agents, scattering operational information. This is why services like CloudWatch, which centrally collect cloud resource health and enable alarms, became important.
CloudWatch gathers metrics, logs, and events from AWS services in one place and builds dashboards and alarms on top of them. You can create high-resolution alarms, inspect logs and metrics side by side, and trigger SNS notifications or automated actions when thresholds are exceeded.
CloudWatch and CloudTrail both help operations, but they watch different things. CloudWatch observes system health and performance metrics, while CloudTrail records which API actions were performed and by whom. If you need to react to current state and thresholds, look at CloudWatch; if you need to trace changes and actions, look at CloudTrail.
Well-suited for nearly every workload where you need to watch operational health, such as CPU spikes, function error rates, queue backlogs, and latency degradation. It is also useful when you want automated remediation based on observed signals. Not a good fit for auditing who called which API.