SOA-C02 Cost and Performance Optimization Practice Question
A SysOps administrator notices that an Amazon RDS DB instance is running at 10% CPU utilization consistently. The instance has 8 vCPUs and 32 GB RAM. The application's performance is adequate. Which action will reduce costs without affecting performance?
⚠ Common exam trap
Watch out — candidates often confuse cost optimization with performance improvement or high availability, leading them to select Multi-AZ or IOPS changes, which increase costs rather than reduce them.
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
✓
Change the DB instance to a smaller instance type.
The DB instance is over-provisioned for the current workload, as evidenced by the consistently low CPU utilization (10%) and adequate application performance. By changing to a smaller instance type, you reduce compute costs directly while maintaining sufficient capacity for the workload. This is the most straightforward cost optimization action when performance requirements are already met.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Multi-AZ deployment for the DB instance.
Why it's wrong here
Enabling Multi-AZ creates a synchronous standby replica in a different Availability Zone, doubling your compute and storage costs because you pay for both the primary and standby instances. This change is designed for high availability and failover, not for cost reduction, and it does nothing to lower the cost of the primary instance. With already low CPU utilization, the additional standby would be even more wasteful.
- ✓
Change the DB instance to a smaller instance type.
Why this is correct
RDS instance pricing is based on the instance class and size, so choosing a smaller class directly reduces the hourly compute charge. Since CPU utilization is consistently low, a smaller instance type can meet the workload's performance requirements while still leaving headroom for spikes. This is the most straightforward and effective way to reduce database costs without sacrificing availability or storage.
- ✗
Change the storage type from gp2 to gp3.
Why it's wrong here
Changing from gp2 to gp3 alters the storage tier, which can reduce storage-related costs and provide better baseline performance, but it does not affect the per-hour compute price of the DB instance. In this scenario the primary cost concern is the underutilized instance size, and storage type changes are not a substitute for right-sizing. Additionally, if the existing gp2 volume is already small or performance is not a bottleneck, the storage savings are likely negligible.
- ✗
Increase the provisioned IOPS.
Why it's wrong here
Increasing provisioned IOPS adds an extra per-IOPS charge on top of the base storage and instance fees, raising total cost rather than lowering it. Low CPU utilization suggests the workload is not compute-bound, and there is no evidence of an I/O bottleneck that would justify additional IOPS. This change is orthogonal to instance pricing, so it cannot address the root cause of an oversized, underused RDS instance.
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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.