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Question 287 of 1,546

Cost and Performance Optimization →mediumMultiple ChoiceObjective-mapped

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 behind an ALB. The application experiences variable traffic, with peak usage during business hours and low traffic at night. The SysOps administrator wants to reduce costs while maintaining performance. The current setup uses On-Demand instances only. The application is stateful and stores session data in an ElastiCache Redis cluster. The administrator has identified that the application can handle Spot Instance interruptions gracefully by redirecting users to a fallback page. The company has a budget of $10,000 per month for EC2 instances, and current costs are $8,000 per month. The administrator wants to reduce costs further without compromising availability for most users. Which solution is MOST cost-effective?

A
Increase the On-Demand base capacity to handle peak load and use Spot for any additional capacity.
Why wrong: Increasing base On-Demand capacity increases costs.
B
Purchase Reserved Instances for the minimum expected capacity and use On-Demand for the rest.
Why wrong: Reserved Instances may not be cost-effective if traffic varies unpredictably.
C
Use only Spot Instances at all times to maximize savings, and rely on the fallback page for interruptions.
Why wrong: During peak hours, Spot interruptions could cause significant user disruption.
D
Use a mixed instances policy with Spot Instances during off-peak hours and On-Demand during peak hours, using Auto Scaling scheduled scaling.
This combines cost savings from Spot with reliability of On-Demand during peak.

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

✓

Use a mixed instances policy with Spot Instances during off-peak hours and On-Demand during peak hours, using Auto Scaling scheduled scaling.

Option D is the most cost-effective because it leverages Spot Instances during off-peak hours (low traffic) to reduce costs significantly while maintaining On-Demand instances during peak hours to ensure performance and availability. Auto Scaling scheduled scaling aligns with the predictable traffic pattern. Option A is less cost-effective because a large On-Demand base capacity would increase costs unnecessarily; Spot can be used more aggressively during off-peak. Option B is not ideal because Reserved Instances require upfront commitment and are best for steady-state workloads, not variable traffic. Option C would risk excessive Spot interruptions during peak hours, degrading user experience despite the fallback page.

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 On-Demand base capacity to handle peak load and use Spot for any additional capacity.
Why it's wrong here
Increasing base On-Demand capacity increases costs.
✗
Purchase Reserved Instances for the minimum expected capacity and use On-Demand for the rest.
Why it's wrong here
Reserved Instances may not be cost-effective if traffic varies unpredictably.
✗
Use only Spot Instances at all times to maximize savings, and rely on the fallback page for interruptions.
Why it's wrong here
During peak hours, Spot interruptions could cause significant user disruption.
✓
Use a mixed instances policy with Spot Instances during off-peak hours and On-Demand during peak hours, using Auto Scaling scheduled scaling.
Why this is correct
This combines cost savings from Spot with reliability of On-Demand during peak.
Related concept
Read the scenario before looking for a memorised answer.

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.

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FAQ

Questions learners often ask

What does this SOA-C02 question test?

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: Use a mixed instances policy with Spot Instances during off-peak hours and On-Demand during peak hours, using Auto Scaling scheduled scaling. — Option D is the most cost-effective because it leverages Spot Instances during off-peak hours (low traffic) to reduce costs significantly while maintaining On-Demand instances during peak hours to ensure performance and availability. Auto Scaling scheduled scaling aligns with the predictable traffic pattern. Option A is less cost-effective because a large On-Demand base capacity would increase costs unnecessarily; Spot can be used more aggressively during off-peak. Option B is not ideal because Reserved Instances require upfront commitment and are best for steady-state workloads, not variable traffic. Option C would risk excessive Spot interruptions during peak hours, degrading user experience despite the fallback page.

What should I do if I get this SOA-C02 question wrong?

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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This SOA-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 SOA-C02 exam.