AWS X-Ray
- What it is
- Distributed tracing service. Follows a single request as it travels through every service in a distributed or microservices application.
- What it gives you
- Service map — a visual graph of services, their dependencies, latency, and error rates.
- Traces — a per-request timeline showing exactly which call was slow or failed.
- Sampling to keep overhead and cost low at high volume.
- Why it matters
- In a monolith, a log tells you where the problem is. Across a dozen services and a Lambda chain, only a trace does.
- Not to be confused with
- Amazon CloudWatch — aggregate metrics and logs (“the service is slow”). X-Ray shows which downstream call caused it.
- AWS CloudTrail — who called the AWS API, an audit record, not application performance.