DVA-C02 Development with AWS Services Practice Question
This DVA-C02 practice question tests your understanding of development with aws services. 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 has an AWS Lambda function that processes messages from an Amazon SQS standard queue. The function is idempotent and currently has a batch size of 10. The developer wants to increase throughput and increases the batch size to 100. After the change, CloudWatch metrics show a significant increase in throttles and the queue backlog is growing. The function's reserved concurrency is set to 10. What is the most effective action to resolve the throttling and improve throughput?
Increase the reserved concurrency of the Lambda function
Higher concurrency allows more invocations to run simultaneously, reducing throttling and enabling the function to consume the larger batch size effectively.
B
Increase the memory allocation of the Lambda function
Why wrong: More memory increases CPU and speed per invocation but does not address the concurrency throttling limit.
C
Switch the SQS queue to a FIFO queue
Why wrong: FIFO queues have lower throughput and are not designed for high-volume processing; this would likely worsen performance.
D
Decrease the batch size back to 10
Why wrong: This would reduce throttling but also reduce the number of messages processed per invocation, thus not improving throughput.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the reserved concurrency of the Lambda function
Increasing the reserved concurrency from 10 to a higher value directly addresses the root cause of throttling. With a batch size of 100, each invocation processes more messages, but the function's reserved concurrency of 10 limits the maximum number of concurrent executions to 10. This means the Lambda service can only invoke the function 10 times at once, regardless of how many messages are in the queue. By raising reserved concurrency, you allow more concurrent invocations to handle the larger batches, reducing throttling and improving throughput.
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 reserved concurrency of the Lambda function
Why this is correct
Higher concurrency allows more invocations to run simultaneously, reducing throttling and enabling the function to consume the larger batch size effectively.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the memory allocation of the Lambda function
Why it's wrong here
More memory increases CPU and speed per invocation but does not address the concurrency throttling limit.
✗
Switch the SQS queue to a FIFO queue
Why it's wrong here
FIFO queues have lower throughput and are not designed for high-volume processing; this would likely worsen performance.
✗
Decrease the batch size back to 10
Why it's wrong here
This would reduce throttling but also reduce the number of messages processed per invocation, thus not improving throughput.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume throttling is due to function performance (memory or CPU) and choose to increase memory, when in fact the issue is a concurrency limit that prevents the function from scaling to handle the larger batch size.
Detailed technical explanation
How to think about this question
Reserved concurrency acts as a hard limit on the number of concurrent Lambda executions for a function, separate from the account-level concurrency limit. When SQS is the event source, Lambda polls the queue and invokes the function with batches; if the function's reserved concurrency is exhausted, subsequent poll requests are throttled (HTTP 429), causing messages to remain in the queue and the backlog to grow. Increasing reserved concurrency allows Lambda to scale up to handle more concurrent batches, but you must also ensure the function's downstream resources (e.g., databases) can handle the increased load to avoid cascading failures.
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.
Development with AWS Services — This question tests Development with AWS Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the reserved concurrency of the Lambda function — Increasing the reserved concurrency from 10 to a higher value directly addresses the root cause of throttling. With a batch size of 100, each invocation processes more messages, but the function's reserved concurrency of 10 limits the maximum number of concurrent executions to 10. This means the Lambda service can only invoke the function 10 times at once, regardless of how many messages are in the queue. By raising reserved concurrency, you allow more concurrent invocations to handle the larger batches, reducing throttling and improving throughput.
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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Question Discussion
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