CloudTrail vs CloudWatch
Compare AWS API audit logging with infrastructure and application monitoring.
Architecture
AWS CloudTrail
CloudTrail records AWS API activity and account-level events. It is primarily used for auditing, governance, compliance, and understanding who changed what in AWS.
Observability
Amazon CloudWatch
CloudWatch provides metrics, logs, dashboards, and alarms for AWS workloads and applications. It is used for operational monitoring, performance visibility, and alerting.
Key Differences
CloudTrail records API activity and account actions, while CloudWatch monitors system behavior, metrics, and logs.
CloudTrail answers 'who did what in AWS', while CloudWatch answers 'how is the system behaving'.
CloudTrail is primarily for audit, governance, and security review, while CloudWatch is primarily for operations and monitoring.
CloudTrail captures events like IAM changes and resource creation, while CloudWatch captures telemetry like CPU usage, latency, errors, and logs.
CloudTrail is essential for compliance and forensic review, while CloudWatch is essential for day-to-day platform reliability and alerting.
Both are often used together because governance and observability solve different operational questions.
When to Use
When to use CloudTrail
Use CloudTrail when you need to track AWS account actions, investigate changes, support compliance, or understand which identity performed a given API action.
When to use CloudWatch
Use CloudWatch when you need to monitor system health, collect logs, trigger alarms, and observe application or infrastructure performance.
Tradeoffs
CloudTrail is excellent for accountability and auditability, but not for runtime operational monitoring.
CloudWatch is excellent for runtime visibility, but not a replacement for API audit history.
Together they provide a more complete operational and governance picture than either tool alone.
Common Mistakes
Trying to use CloudWatch as a replacement for AWS audit history.
Thinking CloudTrail is enough for monitoring application health.
Not separating security and governance questions from reliability and monitoring questions.
Interview Tip
A very clean answer is: CloudTrail is audit, CloudWatch is monitoring.