Troubleshooting and Optimization
Developers observe, debug, and tune applications using CloudWatch and X-Ray. This domain covers logs, metrics, tracing, and caching for performance and cost.
Logging and metrics
Amazon CloudWatch Logs collects application and Lambda logs, while CloudWatch metrics and alarms track behavior over time. Emit custom metrics for business events and use structured JSON logs so they are searchable with CloudWatch Logs Insights. Set alarms that trigger scaling or notifications.
Distributed tracing with X-Ray
AWS X-Ray traces a request as it flows across services, revealing latency and errors at each hop. Instrument code with the X-Ray SDK or enable active tracing on Lambda and API Gateway. Service maps highlight bottlenecks and faulty dependencies that logs alone would not show.
Caching for performance
Reduce latency and cost by caching. Amazon ElastiCache (Redis or Memcached) offloads databases, API Gateway can cache responses, and DynamoDB Accelerator (DAX) provides microsecond reads. Cache invalidation strategy matters: choose a time-to-live that balances freshness against load.
Diagnosing common failures
Throttling appears as HTTP 429 or ProvisionedThroughputExceeded and is addressed with backoff or higher capacity. Access-denied errors point to a missing IAM permission on the execution role. Timeouts may mean an undersized Lambda memory setting or a slow downstream dependency.