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Question 185 of 1,616

Troubleshooting and Optimization →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is to increase the DynamoDB table’s read and write capacity units. This is correct because the Lambda function is being throttled by DynamoDB, as evidenced by the high rate of ProvisionedThroughputExceededException errors, which forces the function to retry operations and drastically increases execution time. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how DynamoDB throttling directly impacts Lambda performance and how to resolve it by scaling capacity, a common trap being that candidates might mistakenly try to optimize the Lambda code or SQS configuration instead. The search intent for Lambda DynamoDB throttling increase capacity is key here: when you see execution time spikes alongside throughput exceptions, always look to the database’s provisioned capacity first. Memory tip: “Throttle means throttle up the RCU/WCU”—if DynamoDB is throwing exceptions, your capacity is the bottleneck, not your code.

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 monitors an AWS Lambda function that processes messages from an Amazon SQS queue. CloudWatch logs show that the function's execution time has increased significantly over the past week. The function's code has not been changed recently. The function makes calls to an Amazon DynamoDB table. CloudWatch metrics show a high rate of DynamoDBProvisionedThroughputExceededException errors. The DynamoDB table has 5 read and 5 write capacity units (RCU/WCU). What is the most effective action to reduce the function's execution time?

Question 1mediummultiple choice

Full question →

A
Increase the Lambda function's memory allocation.
Why wrong: Increasing memory may provide more CPU, but it does not solve the DynamoDB throttling issue. The function is still likely to be throttled when calling the table, leading to retries and increased execution time.
B
Increase the Lambda function's reserved concurrency.
Why wrong: More concurrent invocations would only increase the number of requests to DynamoDB, potentially worsening throttling. It does not reduce execution time for each invocation.
C
Increase the DynamoDB table's read and write capacity units.
Raising the provisioned capacity reduces the frequency of throttling exceptions. With fewer throttles, the function's retries decrease, leading to faster execution and lower overall latency.
D
Increase the Lambda function's timeout.
Why wrong: Increasing the timeout only allows the function to run longer, but it does not address the cause of increased execution time (DynamoDB throttling). The function may still time out if throttling persists.

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 DynamoDB table's read and write capacity units.

Option C is correct because the high rate of DynamoDBProvisionedThroughputExceededException errors indicates that the Lambda function is being throttled by DynamoDB due to insufficient read and write capacity units. This throttling causes the function to retry operations, significantly increasing execution time. Increasing the RCU/WCU from 5 to a higher value directly addresses the bottleneck, allowing operations to complete without retries and reducing overall execution time.

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.

✗
Increase the Lambda function's memory allocation.
Why it's wrong here
Increasing memory may provide more CPU, but it does not solve the DynamoDB throttling issue. The function is still likely to be throttled when calling the table, leading to retries and increased execution time.
✗
Increase the Lambda function's reserved concurrency.
Why it's wrong here
More concurrent invocations would only increase the number of requests to DynamoDB, potentially worsening throttling. It does not reduce execution time for each invocation.
✓
Increase the DynamoDB table's read and write capacity units.
Why this is correct
Raising the provisioned capacity reduces the frequency of throttling exceptions. With fewer throttles, the function's retries decrease, leading to faster execution and lower overall latency.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the Lambda function's timeout.
Why it's wrong here
Increasing the timeout only allows the function to run longer, but it does not address the cause of increased execution time (DynamoDB throttling). The function may still time out if throttling persists.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse performance issues caused by Lambda resource limits (memory, concurrency, timeout) with downstream service throttling, leading them to adjust Lambda settings instead of addressing the root cause in DynamoDB capacity.

Detailed technical explanation

How to think about this question

DynamoDB uses a token bucket algorithm to enforce provisioned throughput; when requests exceed the capacity, it returns a ProvisionedThroughputExceededException (HTTP 400). The AWS SDK automatically retries these errors with exponential backoff, which can add seconds to each operation. In a real-world scenario, a Lambda function processing an SQS batch of 10 messages might experience 10 separate throttling events, each adding 1-3 seconds of delay, ballooning execution time from 200ms to over 30 seconds.

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.

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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 DynamoDB table's read and write capacity units. — Option C is correct because the high rate of DynamoDBProvisionedThroughputExceededException errors indicates that the Lambda function is being throttled by DynamoDB due to insufficient read and write capacity units. This throttling causes the function to retry operations, significantly increasing execution time. Increasing the RCU/WCU from 5 to a higher value directly addresses the bottleneck, allowing operations to complete without retries and reducing overall execution time.

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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Same concept, more angles

1 more ways this is tested on DVA-C02

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A developer monitors an AWS Lambda function that processes messages from an Amazon SQS queue. CloudWatch logs show that the function's execution time has increased significantly over the past week, and it now frequently times out at the 5-minute timeout. The function's code has not been changed recently. The function makes calls to an Amazon DynamoDB table. What is the most likely cause of the increased execution time?

medium

✓ A.The DynamoDB table's read capacity units are underprovisioned, causing throttling.
B.The SQS queue's visibility timeout is too short, causing duplicate processing.
C.The Lambda function's memory is too low, causing CPU throttling.
D.The DynamoDB table's indexes are missing, causing full table scans.

Why A: The most likely cause is that the DynamoDB table's read capacity units are underprovisioned, leading to throttling (ProvisionedThroughputExceededException). When DynamoDB throttles requests, the Lambda function must retry them, which adds latency and can cause the function to exceed its 5-minute timeout. Since the code hasn't changed, this points to a scaling or capacity issue on the DynamoDB side.

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