SOA-C02 Cost and Performance Optimization Practice Question
A SysOps administrator is investigating a cost increase in a production AWS account. They notice that an EC2 instance with a Reservation has been running continuously for months. The instance type is m5.large in us-east-1. The administrator sees that the instance is using a Standard Reserved Instance (RI) that was purchased 6 months ago for a 1-year term. However, the current utilization shows that the instance is only used for 4 hours per day. What should the administrator do to optimize costs without affecting availability?
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
✓
Modify the existing RI to a smaller instance size (e.g., m5.large to m5.xlarge? no, smaller: e.g., t3.medium) and use Auto Scaling with a schedule to start/stop the instance during business hours.
By modifying the existing Standard RI to a smaller instance size (e.g., within the same family or by converting to a Convertible RI to allow family changes), the administrator can better match the actual low utilization pattern. Additionally, using Auto Scaling with a scheduled scaling policy to start and stop the instance during business hours ensures availability during needed times and reduces waste. Option A is incorrect because stopping the instance does not stop the RI charges; Reserved Instance benefits are applied only to running instances, so the RI would be wasted during off-hours. Option B is incorrect because selling the RI on the Reserved Instance Marketplace typically incurs a loss of the upfront payment and does not directly address the over-provisioning issue. Option D is incorrect because converting to a larger instance family would increase compute capacity per hour, leading to higher costs and even more waste given the low utilization.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Stop the instance during off-hours using Instance Scheduler, but keep the RI as-is.
Why it's wrong here
RI benefit applies to running instances; stopping the instance wastes the RI payment for those hours.
- ✗
Sell the current RI on the Reserved Instance Marketplace and purchase a new Convertible RI for a smaller instance type.
Why it's wrong here
Selling the RI may incur loss and does not optimize the current usage pattern.
- ✓
Modify the existing RI to a smaller instance size (e.g., m5.large to m5.xlarge? no, smaller: e.g., t3.medium) and use Auto Scaling with a schedule to start/stop the instance during business hours.
Why this is correct
Modifying RI to a smaller size matches usage; scheduled stop reduces running hours.
- ✗
Convert the RI to a Convertible RI and exchange it for a larger instance family to get more compute per hour.
Why it's wrong here
Larger instance would increase cost, not decrease.
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Same concept, more angles
1 more way 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. A SysOps administrator is optimizing costs for an AWS account. The account has multiple EC2 instances running 24/7 with varying utilization. Which TWO actions will help reduce costs without impacting performance? (Choose TWO.)
medium- ✓ A.Use AWS Compute Optimizer to right-size instances.
- B.Use larger instance types to improve performance.
- C.Enable detailed CloudWatch monitoring for all instances.
- D.Enable termination protection on all instances.
- ✓ E.Purchase Reserved Instances for instances that run consistently.
Why A: AWS Compute Optimizer analyzes historical utilization metrics (CPU, memory, network, etc.) and provides right-sizing recommendations to match instance types to actual workload demands. By downsizing over-provisioned instances, you reduce costs without degrading performance, as the new instance type still meets the workload's peak requirements.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.