DVA-C02 X-Ray service map Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Examine the trace details for exception messages.

  Why this is correct

  Examining X-Ray trace details is the most direct and effective method to diagnose errors within a Lambda function. Each trace provides granular information for segments and subsegments, including full stack traces, precise exception messages, error codes, and specific HTTP status codes for downstream calls. This allows a developer to pinpoint the exact failure point, whether it's within the Lambda's code logic or an issue with an external service call, such as a DynamoDB throttling exception or a permission denied error.

• ✗

  Verify that the Lambda function's IAM role has permissions for X-Ray.

  Why it's wrong here

  Incorrect. Verifying IAM permissions for X-Ray is a prerequisite for sending traces, but since traces are already present, the issue is not about permissions. This action does not help diagnose the errors shown in existing traces.

• ✓

  Check the X-Ray service map for error edges.

  Why this is correct

  Checking the X-Ray service map is an excellent initial step for troubleshooting errors in a distributed application. The service map provides a high-level visual representation of all services involved in an application and their interconnections. Error edges, typically colored red, immediately highlight which specific downstream dependencies (e.g., a DynamoDB table, an SQS queue, or another Lambda function) are experiencing failures when called by the primary Lambda function, quickly isolating the problematic integration point.

• ✗

  Disable X-Ray sampling to capture all requests.

  Why it's wrong here

  Disabling X-Ray sampling to capture 100% of requests is generally not necessary or cost-effective for diagnosing existing errors. X-Ray's default sampling rules are designed to ensure that all requests resulting in errors are captured and traced, even if a lower percentage of successful requests are sampled. Therefore, increasing the sample rate for all requests would primarily increase cost and data volume without providing additional diagnostic information for the errors that are already being captured and traced.

• ✗

  Enable CloudFront to cache responses.

  Why it's wrong here

  Enabling CloudFront to cache responses is a performance optimization for web applications, primarily used to reduce latency and load on origin servers by serving content from edge locations. This action has no relevance to diagnosing errors within a Lambda function using AWS X-Ray. CloudFront operates at the content delivery network (CDN) layer and does not interact with or influence the generation or analysis of X-Ray trace data, which focuses on backend service execution and inter-service communication.