SOA-C02 Cost and Performance Optimization Practice Question
Network Topology
An administrator runs the above CloudWatch command to analyze CPU utilization for an EC2 instance. The instance is currently running with a t3.large instance type. The company wants to optimize costs. Based on the data, which action should the administrator take?
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
✓
Downsize the instance to t3.medium to reduce costs.
The average CPU utilization over the week is low (around 15.5%), indicating the instance is over-provisioned. Downsizing to a t3.medium (half the vCPUs and memory) would likely be sufficient and reduce costs. Reserved Instances would be cost-effective only if the instance runs consistently, but the current utilization is low. Scaling up would increase costs. Stopping the instance is not an option if needed.
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 to save costs immediately.
Why it's wrong here
Stopping the instance would immediately halt compute and free the hourly instance cost, but it is not a valid right-sizing action because the workload still needs to be available (or at least the instance is not expendable). Stopping does not reduce EBS volume or data transfer charges, and if the instance runs critical services, the disruption could cause an outage. The correct response to consistently low CPU is to resize to a smaller instance type, not to stop the instance.
- ✓
Downsize the instance to t3.medium to reduce costs.
Why this is correct
CloudWatch shows low CPU utilization, indicating the t3.large (or current size) is over-provisioned for the actual workload. Downsizing to t3.medium, which has the same vCPU count but half the memory (4 GiB vs 8 GiB), will reduce the on-demand hourly cost while still providing adequate compute for the observed load. Before resizing, confirm memory, network throughput, and application performance remain above the 95th percentile to avoid an undersized instance.
- ✗
Scale up the instance to t3.xlarge to improve performance.
Why it's wrong here
Scaling up to t3.xlarge would increase both vCPUs (to 4) and memory (to 16 GiB), roughly doubling or quadrupling capacity and raising the hourly price. Low CPU utilization proves the instance is not performance-starved, so adding more resources is unnecessary and would increase costs, not improve measurable performance. A scale-up is appropriate only when CloudWatch shows sustained high utilization or throttling, which is not the case here.
- ✗
Purchase a Reserved Instance for the current instance type.
Why it's wrong here
A Reserved Instance (RI) would lower the per-hour rate through a 1- or 3-year commitment, but it does not fix the underlying problem of paying for more capacity than the workload uses. If you purchase an RI for the current t3.large, you are locked into that size and would still pay for idle vCPUs and memory, even with the discount. The financially optimal sequence is to right-size first to match actual utilization, then consider an RI or Savings Plan for the smaller size.
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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.