- A
Use On-Demand instances for the baseline and Spot Instances for any additional capacity.
Why wrong: On-Demand is more expensive than Reserved Instances for predictable baseline. Spot Instances can be reclaimed, so they are not reliable for guaranteed capacity.
- B
Use Reserved Instances for the predicted baseline and On-Demand for any unexpected spikes.
Reserved Instances offer up to 72% discount for consistent usage. On-Demand covers variable capacity needs, providing a cost-effective and flexible solution.
- C
Use Dedicated Hosts for all instances to maximize cost savings.
Why wrong: Dedicated Hosts are typically more expensive than Reserved Instances and are only needed for specific licensing or compliance requirements. They do not optimize cost in this scenario.
- D
Use Spot Instances for all instances to minimize costs.
Why wrong: Spot Instances can be interrupted with little notice, making them unsuitable for a predictable baseline workload that requires high availability.
Quick Answer
The correct answer is to use Reserved Instances for the predicted baseline and On-Demand for any unexpected spikes. This strategy optimizes costs because Reserved Instances offer a significant discount—up to 72%—for steady-state, predictable workloads like the 8 AM to 8 PM baseline load, while On-Demand instances provide the flexibility to handle sudden traffic surges without requiring a long-term commitment. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of balancing cost optimization with capacity planning, often appearing in questions about Auto Scaling groups and purchasing options. A common trap is assuming you should use Spot Instances for the baseline, but Spot Instances can be interrupted and are unsuitable for guaranteed capacity. Memory tip: think of Reserved Instances as your reliable, discounted “base camp” and On-Demand as the flexible “rescue helicopter” for spikes.
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 an e-commerce application on Amazon EC2 instances behind an Auto Scaling group. The application has a predictable baseline load from 8 AM to 8 PM daily and low load overnight. The SysOps administrator wants to optimize costs while ensuring sufficient capacity for the baseline load. Which purchasing option and scaling strategy should the administrator use?
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 Reserved Instances for the predicted baseline and On-Demand for any unexpected spikes.
Option B is correct because Reserved Instances provide a significant discount (up to 72%) over On-Demand for predictable, steady-state workloads like the 8 AM to 8 PM baseline. On-Demand instances then cover any unexpected spikes without requiring upfront commitment, ensuring cost optimization while maintaining capacity for the predictable load.
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.
- ✗
Use On-Demand instances for the baseline and Spot Instances for any additional capacity.
Why it's wrong here
On-Demand is more expensive than Reserved Instances for predictable baseline. Spot Instances can be reclaimed, so they are not reliable for guaranteed capacity.
- ✓
Use Reserved Instances for the predicted baseline and On-Demand for any unexpected spikes.
Why this is correct
Reserved Instances offer up to 72% discount for consistent usage. On-Demand covers variable capacity needs, providing a cost-effective and flexible solution.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use Dedicated Hosts for all instances to maximize cost savings.
Why it's wrong here
Dedicated Hosts are typically more expensive than Reserved Instances and are only needed for specific licensing or compliance requirements. They do not optimize cost in this scenario.
- ✗
Use Spot Instances for all instances to minimize costs.
Why it's wrong here
Spot Instances can be interrupted with little notice, making them unsuitable for a predictable baseline workload that requires high availability.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume Spot Instances are always the cheapest option, but they fail to recognize that the predictable baseline load requires guaranteed availability, which Spot Instances cannot provide due to potential interruptions.
Trap categories for this question
Scenario analysis trap
Dedicated Hosts are typically more expensive than Reserved Instances and are only needed for specific licensing or compliance requirements. They do not optimize cost in this scenario.
Detailed technical explanation
How to think about this question
Reserved Instances require a commitment of 1 or 3 years, with payment options (All Upfront, Partial Upfront, No Upfront) that affect the discount rate; for a predictable daily baseline, a 1-year Partial Upfront Standard RI offers ~40% savings over On-Demand. Auto Scaling can be configured with a mixed instances policy that uses Reserved Instances for the baseline and launches On-Demand for scale-out events, ensuring the RI discount is applied to the steady-state capacity while avoiding over-provisioning. In real-world scenarios, if the baseline load grows unexpectedly, the administrator can modify the RI fleet or purchase additional RIs to cover the new baseline, but On-Demand handles the interim spikes.
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.
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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 Reserved Instances for the predicted baseline and On-Demand for any unexpected spikes. — Option B is correct because Reserved Instances provide a significant discount (up to 72%) over On-Demand for predictable, steady-state workloads like the 8 AM to 8 PM baseline. On-Demand instances then cover any unexpected spikes without requiring upfront commitment, ensuring cost optimization while maintaining capacity for the predictable load.
What should I do if I get this SOA-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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Last reviewed: Jun 11, 2026
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.
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