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Cost and Performance Optimization →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is a mixed instances policy with Spot Instances during off-peak hours and On-Demand during peak hours, using Auto Scaling scheduled scaling. This solution is most cost-effective because it directly aligns compute spending with traffic patterns—Spot Instances, which can be 60-90% cheaper than On-Demand, handle the low-traffic night period where interruptions are tolerable, while On-Demand ensures full performance during business hours when availability is critical. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how to combine Auto Scaling scheduled scaling with a mixed instances policy to optimize cost without sacrificing reliability, a common trap being the assumption that Spot Instances can handle peak traffic or that Reserved Instances are always cheaper for variable workloads. Remember the memory tip: “Peak for On-Demand, sleep on Spot”—use cheaper Spot capacity when traffic is low and interruptions are manageable, and reserve On-Demand for the high-stakes hours.

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?

Question 1mediummultiple choice
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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 C is correct because using Spot Instances only during off-peak hours reduces costs, and moving back to On-Demand during peak ensures performance. Option A is wrong because Spot Instances only during peak could cause interruptions during high traffic. Option B is wrong because Reserved Instances require commitment and may not cover variable traffic. Option D is wrong because a larger base On-Demand capacity increases costs.

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 C is correct because using Spot Instances only during off-peak hours reduces costs, and moving back to On-Demand during peak ensures performance. Option A is wrong because Spot Instances only during peak could cause interruptions during high traffic. Option B is wrong because Reserved Instances require commitment and may not cover variable traffic. Option D is wrong because a larger base On-Demand capacity increases costs.

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.

About these practice questions

Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →

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Same concept, more angles

2 more ways this is tested on SOA-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. An EC2 Auto Scaling group runs a stateless web application with predictable daily peaks. Which two actions can reduce cost while preserving capacity during peak periods? (Choose 2.)

medium
  • ✓ A.Configure scheduled scaling actions for the known peak window.
  • ✓ B.Use a mixed instances policy with some Spot capacity where interruption is acceptable.
  • C.Run all instances as On-Demand at maximum peak size all day.
  • D.Disable health checks to avoid instance replacement.

Why A: Option A is correct because scheduled scaling allows you to proactively increase capacity before the predictable daily peak and reduce it afterward, ensuring you only pay for the resources needed during the peak window. This avoids over-provisioning for the entire day, directly reducing costs while maintaining performance during high-demand periods.

Variation 2. A company runs a web application on EC2 instances behind an ALB. They want to optimize costs for variable traffic patterns while maintaining high availability. Which solution is MOST cost-effective?

medium
  • A.Use Dedicated Hosts to run the application and share resources across multiple accounts.
  • ✓ B.Use a mix of On-Demand and Spot Instances in an Auto Scaling group with a target tracking scaling policy.
  • C.Purchase Reserved Instances for the expected baseline capacity and use On-Demand for spikes.
  • D.Use only On-Demand EC2 Instances with an Auto Scaling group to handle variable traffic.

Why B: Option B is correct because using Spot Instances in an Auto Scaling group with a mix of On-Demand and Spot instances provides cost savings while maintaining availability. Option A is wrong because Reserved Instances require a 1- or 3-year commitment and are not flexible for variable traffic. Option C is wrong because Dedicated Hosts are more expensive and not needed for this use case. Option D is wrong because On-Demand only is more expensive than using Spot.

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Last reviewed: Jun 20, 2026

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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.