The correct answer is to reduce the batch size to 5 and increase the maximum concurrency to 10. This combination directly addresses the root cause of timeouts by lowering the volume of messages each Lambda invocation must process, which reduces overall execution time per function call, while simultaneously increasing parallel invocations to maintain or improve throughput. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how SQS batch size and Lambda concurrency interact under the Lambda polling model—a common trap is assuming that increasing the Lambda timeout alone fixes the issue, but that only masks the problem if individual messages are heavy or processing is slow. A useful memory tip is "less per call, more in parallel," which reminds you that reducing batch size lightens each invocation’s load, and boosting concurrency compensates for the smaller batches by running more functions simultaneously.
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 an AWS Lambda function that processes messages from an Amazon SQS queue. The function is configured with a batch size of 10 and a maximum concurrency of 5. The function frequently reports errors related to message processing timeouts. The function code is idempotent. Which combination of actions will reduce the number of timeouts and improve processing efficiency?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reduce the batch size to 5 and increase the maximum concurrency to 10.
Option D is correct because reducing batch size lowers the work per invocation, and increasing concurrency allows more parallel processing. Option A is wrong because increasing batch size would increase processing time. Option B is wrong because increasing timeout may not solve the root cause if messages are heavy. Option C is wrong because increasing concurrency alone may help but not as much as reducing batch size.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 function timeout to 30 seconds and set the SQS visibility timeout to 6 minutes.
Why it's wrong here
Longer timeout may hide the issue; visibility timeout should be > function timeout.
✗
Increase the batch size to 20 and increase the function timeout to 30 seconds.
Why it's wrong here
Larger batch size increases processing time per invocation.
✓
Reduce the batch size to 5 and increase the maximum concurrency to 10.
Why this is correct
Smaller batches reduce processing time per invocation; more concurrency increases throughput.
Related concept
Static NAT maps one inside address to one outside address.
✗
Increase the maximum concurrency to 10 and set the SQS visibility timeout to 30 seconds.
Why it's wrong here
Higher concurrency helps but visibility timeout too short may cause duplicate processing.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. 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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DVA-C02 NAT questions on configuration and troubleshooting.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Reduce the batch size to 5 and increase the maximum concurrency to 10. — Option D is correct because reducing batch size lowers the work per invocation, and increasing concurrency allows more parallel processing. Option A is wrong because increasing batch size would increase processing time. Option B is wrong because increasing timeout may not solve the root cause if messages are heavy. Option C is wrong because increasing concurrency alone may help but not as much as reducing batch size.
What should I do if I get this DVA-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DVA-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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