Quick Answer
The answer is X-Ray traces across API Gateway and Lambda, combined with CloudWatch Lambda duration and init duration metrics. X-Ray provides end-to-end visibility into request flow, pinpointing where latency accumulates—whether in API Gateway overhead, cold starts, or function execution—while CloudWatch metrics directly measure the time your function spends initializing and running, which are the primary drivers of p95 latency. On the AWS Certified Developer Associate DVA-C02 exam, this question tests your ability to distinguish between diagnostic telemetry and operational metrics; a common trap is to jump to logs first, but duration metrics and traces give you the fastest signal for high p95 latency. Remember the memory tip: “Traces for the path, metrics for the math”—traces show you the route of delay, while metrics quantify the time spent at each stop.
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
An API backed by Lambda returns high p95 latency after deployment. Which two telemetry sources are most useful first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
AWS Billing console only
Why wrong: This does not meet the stated requirement as directly as the correct option.
CloudWatch Lambda duration/init duration/logs
Correct for the stated requirement.
S3 Inventory reports
Why wrong: This does not meet the stated requirement as directly as the correct option.
X-Ray traces across API Gateway and Lambda
Correct for the stated requirement.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
CloudWatch Lambda duration/init duration/logs
CloudWatch Lambda duration and init duration metrics directly measure the time your function spends executing and initializing, which are the primary drivers of p95 latency. Logs can reveal cold starts, timeouts, or inefficient code paths that cause high latency. These are the most immediate telemetry sources to identify performance bottlenecks in the Lambda function itself.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
AWS Billing console only
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
CloudWatch Lambda duration/init duration/logs
Why this is correct
Correct for the stated requirement.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
S3 Inventory reports
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
X-Ray traces across API Gateway and Lambda
Why this is correct
Correct for the stated requirement.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often overlook the combination of CloudWatch metrics and X-Ray traces, mistakenly thinking that only one telemetry source (like CloudWatch logs) is sufficient, or they confuse billing data with performance monitoring.
Detailed technical explanation
Under the hood, Lambda duration is the time from when your code starts executing to when it returns a response, while init duration captures the overhead of creating a new execution environment (cold start). High p95 latency often stems from a small number of cold starts or slow downstream calls, which X-Ray traces can pinpoint by showing the time spent in each service (e.g., API Gateway, Lambda, DynamoDB). In a real-world scenario, a Lambda function that makes an HTTP call to an external API might show high duration in CloudWatch, but only X-Ray reveals that the bottleneck is the external call, not the Lambda code itself.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
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FAQ
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
The correct answer is: CloudWatch Lambda duration/init duration/logs — CloudWatch Lambda duration and init duration metrics directly measure the time your function spends executing and initializing, which are the primary drivers of p95 latency. Logs can reveal cold starts, timeouts, or inefficient code paths that cause high latency. These are the most immediate telemetry sources to identify performance bottlenecks in the Lambda function itself.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.
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