- A
Use async HTTP calls with a callback
Correct. Async calls allow the Lambda function to handle multiple HTTP requests concurrently, reducing overall execution time and preventing timeouts.
- B
Increase the function's timeout to 60 seconds
Why wrong: Increasing timeout may prevent timeouts, but it does not improve efficiency and could increase costs. Also, it does not address the root cause of slow external calls.
- C
Reduce the batch size to 5
Why wrong: Reducing batch size would lower the number of messages processed per invocation, decreasing throughput and potentially increasing cost due to more invocations.
- D
Increase the SQS visibility timeout to 60 seconds
Why wrong: Visibility timeout controls how long a message is hidden from other consumers after being received. It does not affect the Lambda function's execution timeout.
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. 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 developer deployed an AWS Lambda function that is invoked by an Amazon SQS queue. The function is configured with a batch size of 10 and a timeout of 30 seconds. CloudWatch metrics show that the function's Duration is consistently around 28 seconds, but occasionally spikes to 35 seconds causing timeouts. The function makes a synchronous HTTP call to an external API. Which approach will MOST effectively prevent timeouts while maximizing throughput?
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
Use async HTTP calls with a callback
Option A is correct because using async HTTP calls with a callback prevents the Lambda function from blocking on the synchronous HTTP request. This allows the function to process the batch of 10 messages concurrently, reducing the overall execution time below the 30-second timeout even when individual API calls occasionally take longer. By not waiting for each response sequentially, the function maximizes throughput and avoids timeouts.
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.
- ✓
Use async HTTP calls with a callback
Why this is correct
Correct. Async calls allow the Lambda function to handle multiple HTTP requests concurrently, reducing overall execution time and preventing timeouts.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the function's timeout to 60 seconds
Why it's wrong here
Increasing timeout may prevent timeouts, but it does not improve efficiency and could increase costs. Also, it does not address the root cause of slow external calls.
- ✗
Reduce the batch size to 5
Why it's wrong here
Reducing batch size would lower the number of messages processed per invocation, decreasing throughput and potentially increasing cost due to more invocations.
- ✗
Increase the SQS visibility timeout to 60 seconds
Why it's wrong here
Visibility timeout controls how long a message is hidden from other consumers after being received. It does not affect the Lambda function's execution timeout.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume increasing the Lambda timeout or adjusting SQS settings will fix performance issues, when the real problem is synchronous blocking I/O that can be resolved with asynchronous programming to improve concurrency and throughput.
Detailed technical explanation
How to think about this question
Under the hood, Lambda's synchronous HTTP call blocks the execution thread until the response is received, causing the function's Duration to accumulate across all messages in the batch. By using async HTTP calls (e.g., with Python's asyncio or Node.js callbacks/promises), the function can initiate multiple requests concurrently and process responses as they arrive, effectively parallelizing I/O-bound work. This pattern is critical for Lambda functions invoked by SQS with batch sizes >1, as the function must handle all messages within the configured timeout.
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.
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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: Use async HTTP calls with a callback — Option A is correct because using async HTTP calls with a callback prevents the Lambda function from blocking on the synchronous HTTP request. This allows the function to process the batch of 10 messages concurrently, reducing the overall execution time below the 30-second timeout even when individual API calls occasionally take longer. By not waiting for each response sequentially, the function maximizes throughput and avoids timeouts.
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.
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
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