The correct option is AWS X-Ray. It provides distributed tracing that follows a request from Amazon API Gateway through AWS Lambda and into any downstream services so you can identify latency and errors across the full request path.

AWS X-Ray records segments and subsegments for each service and builds a service map that shows latency breakdowns and error counts. You can enable tracing on API Gateway and on Lambda so traces include the API entry point, the authorizer, the Lambda execution, and any calls the function makes to other AWS services or HTTP endpoints. The visual traces and analytics make it straightforward to isolate slow components and to inspect exceptions and stack traces per request.

Amazon CloudWatch is useful for metrics logging dashboards and alarms but it does not provide an end to end distributed trace of a single request across multiple managed services. You should use CloudWatch for logs and metrics and pair it with tracing for request level analysis.

VPC Flow Logs records network flow metadata at the ENI level and helps with IP traffic analysis and connectivity checks. It does not capture application layer traces or the internal function calls that X Ray shows.

Amazon Inspector is a vulnerability assessment service that finds security issues and unintended exposure. It does not provide request tracing or latency analysis and is not suitable for debugging runtime performance problems.

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