DVA-C02 Development with AWS Services Practice Question
This DVA-C02 practice question tests your understanding of development with aws services. 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 working on an application that uses Amazon SQS as a message queue. The application polls the queue using long polling with a wait time of 20 seconds. Recently, the team noticed that messages are being processed multiple times. The application is idempotent, but duplicate processing is causing unnecessary costs. What should the developer do to reduce duplicate message processing?
Use a DynamoDB table to track processed message IDs and ignore duplicates.
This ensures idempotency even if messages are delivered multiple times, effectively reducing the impact of duplicates.
B
Switch to a FIFO queue to enable exactly-once processing.
Why wrong: FIFO queues guarantee exactly-once processing, but the question asks to reduce duplicates, and FIFO may not be necessary; also, FIFO has lower throughput.
C
Increase the visibility timeout to a value greater than the maximum processing time.
Why wrong: This reduces the chance of duplicates but does not eliminate them if the consumer crashes after the timeout.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a DynamoDB table to track processed message IDs and ignore duplicates.
Option D is correct. Enabling the visibility timeout to be at least as long as the processing time ensures that if the consumer fails to delete the message within the visibility timeout, the message becomes visible again, causing duplicates. Option A is wrong because SQS already provides at-least-once delivery; deduplication is not natively supported for standard queues. Option B is wrong because increasing the visibility timeout helps but does not eliminate duplicates entirely. Option C is wrong because FIFO queues provide exactly-once processing but may not be suitable if the application requires higher throughput or ordering not needed.
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.
✓
Use a DynamoDB table to track processed message IDs and ignore duplicates.
Why this is correct
This ensures idempotency even if messages are delivered multiple times, effectively reducing the impact of duplicates.
Related concept
Static NAT maps one inside address to one outside address.
✗
Switch to a FIFO queue to enable exactly-once processing.
Why it's wrong here
FIFO queues guarantee exactly-once processing, but the question asks to reduce duplicates, and FIFO may not be necessary; also, FIFO has lower throughput.
✗
Increase the visibility timeout to a value greater than the maximum processing time.
Why it's wrong here
This reduces the chance of duplicates but does not eliminate them if the consumer crashes after the timeout.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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.
Development with AWS Services — This question tests Development with AWS Services — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use a DynamoDB table to track processed message IDs and ignore duplicates. — Option D is correct. Enabling the visibility timeout to be at least as long as the processing time ensures that if the consumer fails to delete the message within the visibility timeout, the message becomes visible again, causing duplicates. Option A is wrong because SQS already provides at-least-once delivery; deduplication is not natively supported for standard queues. Option B is wrong because increasing the visibility timeout helps but does not eliminate duplicates entirely. Option C is wrong because FIFO queues provide exactly-once processing but may not be suitable if the application requires higher throughput or ordering not needed.
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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