The answer is the HTTP client’s timeout set to a low value, most commonly the default 3-second timeout found in libraries like Node.js `http` or Python `requests`. This is correct because the Lambda function’s configured timeout of 10 seconds never gets a chance to fire; instead, the HTTP client’s internal timeout expires first, causing the function to throw an error and appear to time out at exactly 3 seconds. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your ability to distinguish between a Lambda timeout and a client-side timeout—a common trap where engineers mistakenly increase the Lambda timeout setting without checking the HTTP client configuration. The key insight is that a lambda timeout due to http client timeout always presents with a consistent, short failure time that matches the client’s default, not the function’s configured limit. Memory tip: think “client clock beats Lambda clock”—the inner timeout always wins.
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. 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 troubleshooting a Lambda function that times out after 3 seconds. The function makes an HTTP request to an external API. The function's timeout setting is 10 seconds. What is the most likely cause of the timeout?
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 HTTP client's timeout is set to a low value.
The Lambda function times out after exactly 3 seconds, which is a common default HTTP client timeout (e.g., 3 seconds in the Node.js `http` module or Python `requests` library). Even though the Lambda function's configured timeout is 10 seconds, the HTTP client's internal timeout fires first, causing the function to fail before the Lambda timeout is reached. This is the most likely cause because the symptom matches a client-side timeout rather than a server-side or infrastructure issue.
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 external API is throttling the request.
Why it's wrong here
Throttling would return an error, not a timeout.
✓
The HTTP client's timeout is set to a low value.
Why this is correct
Default HTTP client timeout is often 3 seconds; needs to be increased.
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 Lambda function is not in a VPC.
Why it's wrong here
Not being in a VPC does not cause timeouts; it affects network access.
✗
The Lambda function's memory is insufficient.
Why it's wrong here
Insufficient memory would cause performance issues, not a consistent 3-second timeout.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the Lambda function's configured timeout (10 seconds) is the only timeout that matters, overlooking that application-level timeouts (like HTTP client timeouts) can fire independently and cause earlier failures.
Detailed technical explanation
How to think about this question
HTTP clients in Lambda runtimes (e.g., Node.js `http.request`, Python `requests`, Java `HttpURLConnection`) often have a default connection or read timeout of 3 seconds. When the external API is slow or unresponsive, the client throws a timeout error (e.g., `socket hang up` or `ReadTimeoutError`) after that duration, which the Lambda runtime catches and terminates the invocation. This is distinct from the Lambda function's configured timeout, which is enforced by the AWS Lambda service at the execution environment level. In practice, always set the HTTP client timeout to be less than the Lambda timeout to allow for retries or graceful error handling.
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.
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 HTTP client's timeout is set to a low value. — The Lambda function times out after exactly 3 seconds, which is a common default HTTP client timeout (e.g., 3 seconds in the Node.js `http` module or Python `requests` library). Even though the Lambda function's configured timeout is 10 seconds, the HTTP client's internal timeout fires first, causing the function to fail before the Lambda timeout is reached. This is the most likely cause because the symptom matches a client-side timeout rather than a server-side or infrastructure issue.
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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