How do you monitor a Lambda function’s performance?

Difficulty: 6/10

CloudWatch Metrics, X-Ray Tracing, Logging

Monitoring the performance of a Lambda function is crucial for identifying bottlenecks, debugging failures, and optimizing cost. AWS provides built-in tools like Amazon CloudWatch, AWS X-Ray, and Lambda Insights to help you track execution metrics, logs, and traces.

Ways to Monitor Lambda Performance

1
Amazon CloudWatch Logs: Captures logs generated by the function (e.g., console.log, print).
2
Amazon CloudWatch Metrics: Provides key metrics such as invocation count, duration, errors, throttles, and concurrent executions.
3
AWS X-Ray: Enables distributed tracing of requests across AWS services to pinpoint latency issues.
4
CloudWatch Alarms: Alerts you when metrics cross thresholds (e.g., high error rate or duration).
5

Enabling X-Ray Tracing via AWS CLI

Scenario Questions

0-2 years experience

2-5 years experience

1Your team added a new third‑party library and suddenly the Lambda’s average duration doubled. Walk me through how you would investigate and confirm the performance regression using AWS tools.

Follow-up Questions