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Question 370 of 1,616

Troubleshooting and Optimization →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is to increase the read and write capacity units on the DynamoDB table, as the throttling is caused by insufficient provisioned throughput to handle the Lambda function’s concurrency of 100. When a Lambda function with reserved concurrency exceeds the table’s 5 RCUs and 5 WCUs, DynamoDB returns throttle events that directly increase latency, because each throttled request must be retried. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding that DynamoDB capacity must scale with Lambda concurrency; a common trap is to assume that Lambda retries or error handling alone will fix latency, but the root cause is the table’s throughput ceiling. The most effective solution is to provision higher RCUs and WCUs to match the request volume, which eliminates the bottleneck without reducing concurrency. Memory tip: “Lambda concurrency drives DynamoDB capacity—match the throughput to avoid the throttle.”

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 a new version of an AWS Lambda function that is part of a serverless application. The function uses an Amazon DynamoDB table as a data store. After deployment, the developer notices that the function's latency has increased significantly for some requests. CloudWatch traces show that the increase is due to DynamoDB throttle events. The function is configured with a reserved concurrency of 100 and the DynamoDB table has 5 read capacity units (RCUs) and 5 write capacity units (WCUs). What is the most effective way to reduce the throttling while maintaining application performance?

Question 1hardmultiple choice

Full question →

A
Decrease the reserved concurrency of the Lambda function to 10
Why wrong: Reducing concurrency limits the number of concurrent executions but does not increase the capacity of the DynamoDB table, so throttling may still occur with fewer but still load-intensive requests.
B
Increase the read and write capacity units on the DynamoDB table
Increasing RCU and WCU directly increases the number of operations the table can handle, reducing throttling.
C
Enable DynamoDB Accelerator (DAX) for caching reads
Why wrong: DAX only caches reads, not writes, and does not address write throttling. Also, it adds complexity.
D
Enable auto scaling on the DynamoDB table
Why wrong: Auto scaling adjusts capacity over time but requires a starting point; with only 5 units, it may not react fast enough to sudden spikes. Manual increase is more immediate.

Full breakdown with real-world context →

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

✓

Increase the read and write capacity units on the DynamoDB table

The primary cause of the throttling is insufficient DynamoDB capacity to handle the request volume from the Lambda function. Increasing the read and write capacity units (RCUs/WCUs) directly addresses the throttle events by providing more throughput to match the function's concurrency of 100. This is the most effective solution because it resolves the bottleneck at the data store level without reducing the application's ability to process requests concurrently.

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.

✗
Decrease the reserved concurrency of the Lambda function to 10
Why it's wrong here
Reducing concurrency limits the number of concurrent executions but does not increase the capacity of the DynamoDB table, so throttling may still occur with fewer but still load-intensive requests.
✓
Increase the read and write capacity units on the DynamoDB table
Why this is correct
Increasing RCU and WCU directly increases the number of operations the table can handle, reducing throttling.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable DynamoDB Accelerator (DAX) for caching reads
Why it's wrong here
DAX only caches reads, not writes, and does not address write throttling. Also, it adds complexity.
✗
Enable auto scaling on the DynamoDB table
Why it's wrong here
Auto scaling adjusts capacity over time but requires a starting point; with only 5 units, it may not react fast enough to sudden spikes. Manual increase is more immediate.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates may choose auto scaling (Option D) thinking it dynamically handles spikes, but they overlook that auto scaling has a significant lag and cannot prevent immediate throttling, whereas increasing the base capacity is the immediate and effective solution.

Detailed technical explanation

How to think about this question

DynamoDB throttle events occur when request rates exceed the provisioned RCUs or WCUs for a table. Each RCU provides one strongly consistent read per second for items up to 4 KB, and each WCU provides one write per second for items up to 1 KB. With 5 RCUs and 5 WCUs, the table can handle only 5 reads or 5 writes per second, which is easily overwhelmed by a Lambda function with 100 reserved concurrency, as each invocation may perform multiple read/write operations. Increasing capacity units is the direct fix, while auto scaling would require time to scale up and might not prevent throttling during burst traffic.

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 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.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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: Increase the read and write capacity units on the DynamoDB table — The primary cause of the throttling is insufficient DynamoDB capacity to handle the request volume from the Lambda function. Increasing the read and write capacity units (RCUs/WCUs) directly addresses the throttle events by providing more throughput to match the function's concurrency of 100. This is the most effective solution because it resolves the bottleneck at the data store level without reducing the application's ability to process requests concurrently.

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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This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.