The answer is to use a mix of On-Demand and Spot Instances in the Auto Scaling group, combined with dynamic scaling based on CPU utilization and an Elastic Load Balancer with connection draining. This approach directly addresses both cost and performance optimization with Auto Scaling by leveraging Spot Instances for significant savings during variable traffic, while On-Demand Instances ensure baseline reliability. Dynamic scaling adjusts capacity in real-time to match demand, preventing over-provisioning, and connection draining gracefully terminates instances during scale-in to avoid dropping active requests. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of balancing cost efficiency with high availability—a common trap is assuming larger instance sizes or reducing instance count will solve the problem, but those actions increase cost or risk performance degradation. Remember the memory tip: "Mix, match, and drain" to recall the three pillars of mixing instance types, matching demand with dynamic scaling, and draining connections during scale-in.
SOA-C02 Cost and Performance Optimization Practice Question
This SOA-C02 practice question tests your understanding of cost and performance optimization. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 runs a web application on EC2 instances in an Auto Scaling group. The application experiences variable traffic. The company wants to improve performance and reduce costs. Which THREE actions should the company take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement dynamic scaling policies based on CPU utilization.
Using a mix of On-Demand and Spot Instances balances cost and reliability. Implementing dynamic scaling based on CPU utilization ensures capacity matches demand. Using an ELB with connection draining helps maintain performance during scale-in. Increasing instance size increases cost. Reducing the number of instances may cause performance issues.
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.
✓
Implement dynamic scaling policies based on CPU utilization.
Why this is correct
Dynamic scaling adjusts capacity in real-time.
Related concept
Read the scenario before looking for a memorised answer.
✗
Reduce the number of instances in the Auto Scaling group to lower costs.
Why it's wrong here
Reducing instances may cause performance issues.
✓
Use an Application Load Balancer with connection draining.
Why this is correct
Connection draining ensures in-flight requests complete during scale-in.
Related concept
Read the scenario before looking for a memorised answer.
✓
Use a mix of On-Demand and Spot Instances in the Auto Scaling group.
Why this is correct
This reduces cost while maintaining reliability.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the instance size to handle peak load.
Why it's wrong here
Increasing instance size increases 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: Implement dynamic scaling policies based on CPU utilization. — Using a mix of On-Demand and Spot Instances balances cost and reliability. Implementing dynamic scaling based on CPU utilization ensures capacity matches demand. Using an ELB with connection draining helps maintain performance during scale-in. Increasing instance size increases cost. Reducing the number of instances may cause performance issues.
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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