- A
The Lambda function is experiencing cold starts due to low invocation frequency.
Why wrong: Cold starts increase Lambda duration, not integration latency. Integration latency is the network time, not the function execution time.
- B
The DynamoDB on-demand capacity is throttling requests.
Why wrong: Throttling would cause Lambda to retry, increasing its duration and possibly leading to timeouts, but it would not directly affect integration latency.
- C
The external API call is adding network latency due to its geographic location.
Why wrong: Latency from the external API call is included in the Lambda function duration, not in integration latency. Integration latency specifically measures API Gateway to Lambda round-trip time.
- D
The API Gateway request/response payload size is large, increasing transfer time.
Large payloads take longer to transfer between API Gateway and Lambda, increasing integration latency even if the Lambda function executes quickly.
Quick Answer
The answer is a large request or response payload size, which increases transfer time between API Gateway and Lambda. This is correct because API Gateway integration latency measures the total time for data to travel over the HTTPS connection, including network overhead from serializing and deserializing large payloads, while Lambda duration only tracks the time your function code actually executes. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your ability to distinguish between network-level delays and compute-level performance—a common trap is assuming the Lambda function itself is slow when the bottleneck is actually in the data transfer layer. Remember that Lambda’s billed duration excludes network I/O time, so if you see high integration latency paired with low Lambda duration, always suspect payload size as the culprit. A useful memory tip: “Big payloads, big transfer time—Lambda’s clock stops at the function line.”
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. 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 developer is troubleshooting slow response times in a serverless application. The application consists of an Amazon API Gateway REST API that invokes an AWS Lambda function, which then writes data to an Amazon DynamoDB table with on-demand capacity. The function also calls an external API for enrichment. The developer observes that the API Gateway integration latency is high, but the Lambda function duration is low. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The API Gateway request/response payload size is large, increasing transfer time.
Option D is correct because high API Gateway integration latency combined with low Lambda duration indicates that the delay is occurring in the data transfer between API Gateway and Lambda, not within the function itself. A large request/response payload increases the network transfer time over the HTTPS connection, which is measured as part of integration latency but not reflected in the function's billed duration.
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.
- ✗
The Lambda function is experiencing cold starts due to low invocation frequency.
Why it's wrong here
Cold starts increase Lambda duration, not integration latency. Integration latency is the network time, not the function execution time.
- ✗
The DynamoDB on-demand capacity is throttling requests.
Why it's wrong here
Throttling would cause Lambda to retry, increasing its duration and possibly leading to timeouts, but it would not directly affect integration latency.
- ✗
The external API call is adding network latency due to its geographic location.
Why it's wrong here
Latency from the external API call is included in the Lambda function duration, not in integration latency. Integration latency specifically measures API Gateway to Lambda round-trip time.
- ✓
The API Gateway request/response payload size is large, increasing transfer time.
Why this is correct
Large payloads take longer to transfer between API Gateway and Lambda, increasing integration latency even if the Lambda function executes quickly.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'integration latency' with 'Lambda duration' and assume the issue must be inside the function (cold starts, throttling, or external calls), rather than recognizing that integration latency specifically captures network transfer time between API Gateway and the backend.
Detailed technical explanation
How to think about this question
API Gateway integration latency is the time from when API Gateway sends the request to the backend (Lambda) until it receives the complete response. This includes network round-trip time and data serialization/deserialization. The Lambda duration metric, on the other hand, measures only the time your function code executes, excluding the time spent transferring the payload over the network. For large payloads (e.g., >1 MB), the transfer time can dominate integration latency even if the function itself runs quickly.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
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Troubleshooting and Optimization — study guide chapter
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The API Gateway request/response payload size is large, increasing transfer time. — Option D is correct because high API Gateway integration latency combined with low Lambda duration indicates that the delay is occurring in the data transfer between API Gateway and Lambda, not within the function itself. A large request/response payload increases the network transfer time over the HTTPS connection, which is measured as part of integration latency but not reflected in the function's billed duration.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
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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