The answer is Amazon CloudWatch Metrics and AWS X-Ray. CloudWatch Metrics provides built-in Lambda duration and invocation counts, allowing you to spot performance trends and identify abnormally slow executions, while X-Ray traces individual requests and explicitly reveals cold starts by showing the initialization phase duration in its service map and traces. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this pairing tests your understanding that CloudWatch gives aggregate performance data, but only X-Ray can isolate the cold start penalty at the request level—a common trap is choosing CloudWatch Logs alone, which stores raw logs but lacks the structured tracing needed to pinpoint initialization overhead. Remember the memory tip: “Metrics for the big picture, X-Ray for the cold picture.”
DOP-C02 Monitoring and Logging Practice Question
This DOP-C02 practice question tests your understanding of monitoring and logging. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A DevOps engineer is investigating a performance issue in a serverless application using AWS Lambda. The engineer wants to view the duration of each invocation and identify cold starts. Which TWO AWS services should be used? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Amazon CloudWatch Metrics for Lambda (duration, invocations)
Amazon CloudWatch Metrics for Lambda (option A) provides built-in metrics such as duration and invocations, which are essential for analyzing performance trends and identifying slow invocations. AWS X-Ray (option B) traces individual requests through the Lambda function and can explicitly detect cold starts by showing the initialization phase duration, making it the correct complementary service.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Amazon CloudWatch Metrics for Lambda (duration, invocations)
Why this is correct
CloudWatch Metrics shows duration and invocation counts.
Related concept
Read the scenario before looking for a memorised answer.
✗
AWS X-Ray to trace invocations and detect cold starts
Why it's wrong here
X-Ray can show cold starts, but the question asks for TWO; the pair of CloudWatch Metrics and Logs is more direct.
✗
AWS CloudTrail to record Lambda API calls
Why it's wrong here
CloudTrail records API calls, not performance metrics.
✓
Amazon CloudWatch Logs for Lambda execution logs
Why this is correct
CloudWatch Logs contains logs that indicate cold starts.
Related concept
Read the scenario before looking for a memorised answer.
✗
AWS Config to track Lambda configuration changes
Why it's wrong here
Config tracks configuration, not performance.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume CloudWatch Logs (option D) is needed for performance analysis, but Lambda execution logs contain custom log output and error messages, not structured duration or cold start data—those are provided by CloudWatch Metrics and X-Ray respectively.
Trap categories for this question
Command / output trap
X-Ray can show cold starts, but the question asks for TWO; the pair of CloudWatch Metrics and Logs is more direct.
Detailed technical explanation
How to think about this question
Cold starts occur when Lambda initializes a new execution environment, adding a latency overhead that can be observed in X-Ray traces as an 'Init' segment before the function's 'Invocation' segment. CloudWatch Metrics aggregates duration across all invocations but does not separate cold start vs. warm start durations; X-Ray's per-trace view is required to isolate cold start events. The combination of CloudWatch Metrics for aggregate performance monitoring and X-Ray for granular, per-request diagnostics is the standard approach for Lambda performance troubleshooting.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Monitoring and Logging — This question tests Monitoring and Logging — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon CloudWatch Metrics for Lambda (duration, invocations) — Amazon CloudWatch Metrics for Lambda (option A) provides built-in metrics such as duration and invocations, which are essential for analyzing performance trends and identifying slow invocations. AWS X-Ray (option B) traces individual requests through the Lambda function and can explicitly detect cold starts by showing the initialization phase duration, making it the correct complementary service.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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