DVA-C02 Troubleshooting and Optimization Practice Question
A developer is using AWS X-Ray to trace requests through a microservices application. One of the services, Service B, is not appearing in the trace map. What is the MOST likely reason?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Service B is not instrumented with the X-Ray SDK.
For X-Ray to trace requests across services, each service must be instrumented with the X-Ray SDK. If Service B is not instrumented, it won't send trace data, and it won't appear in the trace map.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Service B is using HTTP/2, which is not supported by X-Ray.
Why it's wrong here
X-Ray SDKs are designed to automatically capture incoming and outgoing HTTP/2 requests and responses, generating appropriate segments and subsegments. Therefore, Service B using HTTP/2 would not inherently prevent it from appearing on the X-Ray service map, assuming it is otherwise correctly instrumented. This option is incorrect because X-Ray fully supports tracing applications that communicate via HTTP/2.
- ✗
Service B is running in a different AWS region.
Why it's wrong here
X-Ray is designed for distributed tracing across complex architectures, including those spanning multiple AWS regions. As long as Service B is properly instrumented with the X-Ray SDK and configured to send its trace data to an X-Ray endpoint, its segments will be integrated into the overall trace. The X-Ray service map can seamlessly visualize cross-region interactions, provided the trace context is propagated correctly.
- ✗
The X-Ray sampling rate is set too low.
Why it's wrong here
While a very low X-Ray sampling rate would significantly reduce the number of traces captured for Service B, it would not completely eliminate it from the service map. If Service B is instrumented and actively processing requests, some of those requests would eventually be sampled and traced. This would result in Service B appearing on the map, albeit perhaps infrequently, rather than being entirely absent.
- ✓
Service B is not instrumented with the X-Ray SDK.
Why this is correct
The X-Ray SDK is fundamental for any service to participate in distributed tracing. It's responsible for generating trace segments, capturing metadata, and propagating the trace context to downstream services. Without the X-Ray SDK integrated into Service B's code, the service cannot generate or send any trace data to the X-Ray daemon or service, thus preventing it from appearing on the service map.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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