DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 company uses AWS Lambda functions behind an Amazon API Gateway REST API. During an incident, the API returns 502 Bad Gateway errors. The Lambda function logs show no errors. 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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Lambda function is returning a response that exceeds the API Gateway payload size limit
When an API GatewayREST API returns 502 Bad Gateway errors but the Lambda function logs show no errors, the most likely cause is that the Lambda function is returning a response that exceeds the API Gateway payload size limit. API Gateway has a maximum payload size of 10 MB for REST APIs, and if the Lambda function returns a response larger than this, API Gateway will reject it and return a 502 error without the Lambda function itself throwing an exception or logging an error.
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 throwing an unhandled exception
Why it's wrong here
Logs show no errors, so exceptions are not the issue.
✓
The Lambda function is returning a response that exceeds the API Gateway payload size limit
Why this is correct
API Gateway has a 10 MB payload limit; exceeding it causes 502.
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.
✗
The API Gateway has reached its maximum concurrency limit
Why it's wrong here
Concurrency limits cause 429, not 502.
✗
The Lambda function is timing out and API Gateway is not handling the timeout correctly
Why it's wrong here
Timeouts cause 504, not 502.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the distinction between different HTTP status codes (502 vs 504 vs 429) and the specific conditions under which each is returned, leading candidates to incorrectly attribute 502 errors to Lambda timeouts or API Gateway throttling instead of payload size limits.
Trap categories for this question
Command / output trap
Logs show no errors, so exceptions are not the issue.
Detailed technical explanation
How to think about this question
API GatewayREST APIs enforce a 10 MB payload size limit for both request and response, and this limit is checked after the Lambda function completes execution. If the response exceeds this limit, API Gateway returns a 502 error without invoking the Lambda function's error handling or logging, which explains why the Lambda logs show no errors. This behavior is distinct from the 6 MB limit for HTTP APIs and the 256 KB limit for synchronous Lambda invocation payloads, making it a common pitfall when processing large datasets or binary content.
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.
Incident and Event Response — This question tests Incident and Event Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Lambda function is returning a response that exceeds the API Gateway payload size limit — When an API Gateway REST API returns 502 Bad Gateway errors but the Lambda function logs show no errors, the most likely cause is that the Lambda function is returning a response that exceeds the API Gateway payload size limit. API Gateway has a maximum payload size of 10 MB for REST APIs, and if the Lambda function returns a response larger than this, API Gateway will reject it and return a 502 error without the Lambda function itself throwing an exception or logging an error.
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.
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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Question Discussion
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