The correct answer is to refactor the Lambda function to use asynchronous invocation, return a 202 Accepted immediately, and have the client poll for results. This resolves the API Gateway 504 timeout because the default integration timeout of 29 seconds is hard-capped, and your backend Lambda occasionally runs up to 30 seconds. By switching to async invocation, the API Gateway triggers the Lambda without waiting for it to finish, returning a 202 response well within the timeout window, while the client polls a separate status endpoint—like a DynamoDB record or S3 presigned URL—for the final result. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of decoupling synchronous API calls from long-running processes; a common trap is trying to increase the timeout or use synchronous invocation with a longer Lambda execution, which still hits the 29-second Gateway limit. Remember the mnemonic: “202 buys you time, async frees the 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. A key principle to apply: aPI Gateway integration timeout has a hard limit of 29 seconds.. 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 an Amazon API Gateway REST API that returns 504 Gateway Timeout errors for certain requests. The backend is a Lambda function that performs a resource-intensive operation that occasionally takes up to 30 seconds. API Gateway has a default integration timeout of 29 seconds. The developer cannot reduce the execution time. What should the developer do to resolve the timeout issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Refactor the Lambda function to use asynchronous invocation, return a 202 immediately, and have the client poll for results.
Option B is correct because it decouples the client from the long-running Lambda execution. By invoking the Lambda asynchronously, the API Gateway can return a 202 Accepted response immediately, well within the 29-second integration timeout. The client then polls a separate endpoint (e.g., using a presigned S3 URL or a DynamoDB status record) to retrieve the final result, completely sidestepping the timeout limitation.
Key principle: API Gateway integration timeout has a hard limit of 29 seconds.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Increase the API Gateway integration timeout to 30 seconds.
Why it's wrong here
The maximum integration timeout for API Gateway is 29 seconds; it cannot be increased.
✓
Refactor the Lambda function to use asynchronous invocation, return a 202 immediately, and have the client poll for results.
Why this is correct
Correct. Asynchronous processing avoids the timeout by decoupling the request from the long-running work.
Related concept
API Gateway integration timeout has a hard limit of 29 seconds.
✗
Enable API Gateway caching to avoid repeated calls.
Why it's wrong here
Caching helps with repeated identical requests but does not solve the timeout for unique requests.
✗
Use multiple Lambda functions to parallelize processing.
Why it's wrong here
Parallelization might reduce total time but each individual invocation could still exceed 29 seconds.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the integration timeout is configurable to any value, but AWS enforces a hard 29-second limit for REST APIs, making Option A technically impossible.
Detailed technical explanation
How to think about this question
Under the hood, API Gateway's integration timeout is enforced at the network layer—the service will close the TCP connection after 29 seconds if no response is received from the backend. Asynchronous Lambda invocation returns a 202 immediately and places the event in an internal SQS queue, allowing the function to run for up to 15 minutes (the maximum Lambda timeout). A common real-world pattern is to store the result in DynamoDB or S3 and expose a separate GET endpoint for the client to poll until the status changes to 'COMPLETE'.
KKey Concepts to Remember
API Gateway integration timeout has a hard limit of 29 seconds.
Asynchronous processing decouples long-running tasks from immediate API responses.
A 202 Accepted status indicates a request has been received for processing.
Clients can poll a separate endpoint to retrieve results of asynchronous operations.
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
API Gateway integration timeout has a hard limit of 29 seconds.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review aPI Gateway integration timeout has a hard limit of 29 seconds., then practise related DVA-C02 questions on the same topic to reinforce the concept.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — API Gateway integration timeout has a hard limit of 29 seconds..
What is the correct answer to this question?
The correct answer is: Refactor the Lambda function to use asynchronous invocation, return a 202 immediately, and have the client poll for results. — Option B is correct because it decouples the client from the long-running Lambda execution. By invoking the Lambda asynchronously, the API Gateway can return a 202 Accepted response immediately, well within the 29-second integration timeout. The client then polls a separate endpoint (e.g., using a presigned S3 URL or a DynamoDB status record) to retrieve the final result, completely sidestepping the timeout limitation.
What should I do if I get this DVA-C02 question wrong?
Review aPI Gateway integration timeout has a hard limit of 29 seconds., then practise related DVA-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
API Gateway integration timeout has a hard limit of 29 seconds.
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