4.3. Monitoring and Maintaining Pipelines

Robust monitoring provides visibility into the health and performance of your data pipelines, allowing you to detect failures and performance bottlenecks before they impact downstream consumers. By leveraging services like CloudWatch and CloudTrail, you can create a comprehensive audit and alerting system to maintain operational excellence.

💡 First Principle: Consider a nightly ETL that silently fails for three days — by the time someone notices, the executive dashboard has been showing stale data to the board. A pipeline without monitoring fails silently. Think of it like a factory without quality sensors — everything looks fine from the outside until customers start receiving defective products. Without CloudWatch alarms, CloudTrail audit trails, and proactive alerting, data engineers discover pipeline failures only when stakeholders complain about stale or incorrect data — often hours or days after the problem started.

Monitoring answers three questions: Is the pipeline running? (execution metrics), Is the data correct? (quality checks), and Who did what? (audit logging). The exam tests all three, with particular emphasis on CloudWatch for operational monitoring and CloudTrail for security auditing. What's the first thing you check when a Glue job fails? The CloudWatch Logs for the job execution — not the Glue console.