The answer is to increase reserved concurrency to 1000 and enable batch processing with a batch size of 10 in the SQS event source mapping. This resolves Lambda throttling from SQS spikes by allowing the function to scale to handle the full 10,000 messages per second burst, while batch processing reduces the number of invocations by processing up to 10 messages per execution, directly optimizing cost. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of Lambda concurrency and SQS batch processing throttling cost optimization trade-offs—a common trap is thinking that reducing concurrency or switching to EC2 will help, but the key is balancing scaling with invocation efficiency. Remember the memory tip: “Batch to slash invocations, concurrency to crush spikes.”
SOA-C02 Cost and Performance Optimization Practice Question
This SOA-C02 practice question tests your understanding of cost and performance 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 company uses AWS Lambda functions to process messages from an SQS queue. The Lambda function is configured with a reserved concurrency of 100. The SQS queue receives unpredictable spikes of up to 10,000 messages per second. The function takes about 1 second to process a message. The SysOps team notices that during spikes, messages are being throttled and appear in the DLQ. How can the team resolve this while optimizing cost?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase reserved concurrency to 1000 and enable batch processing with a batch size of 10 in the SQS event source mapping.
Option D is correct because increasing reserved concurrency allows Lambda to scale to handle the spike, and using batch processing reduces the number of invocations, lowering cost. Option A is wrong because reducing concurrency would worsen throttling. Option B is wrong because a larger instance type might not be available and increases cost per invocation. Option C is wrong because Lambda cannot be run on EC2 in a serverless manner.
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.
✗
Reduce the reserved concurrency to 10 to force the function to process messages more slowly.
Why it's wrong here
This would increase throttling and DLQ messages.
✓
Increase reserved concurrency to 1000 and enable batch processing with a batch size of 10 in the SQS event source mapping.
Read the scenario before looking for a memorised answer.
✗
Provision an EC2 fleet to poll the SQS queue and invoke the Lambda function.
Why it's wrong here
This adds complexity and cost, defeating serverless benefits.
✗
Increase the Lambda function memory and timeout to use a larger instance type.
Why it's wrong here
Larger instances may not help with concurrency limits and increase cost.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Cost and Performance Optimization — This question tests Cost and Performance Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase reserved concurrency to 1000 and enable batch processing with a batch size of 10 in the SQS event source mapping. — Option D is correct because increasing reserved concurrency allows Lambda to scale to handle the spike, and using batch processing reduces the number of invocations, lowering cost. Option A is wrong because reducing concurrency would worsen throttling. Option B is wrong because a larger instance type might not be available and increases cost per invocation. Option C is wrong because Lambda cannot be run on EC2 in a serverless manner.
What should I do if I get this SOA-C02 question wrong?
Identify which SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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