SOA-C02 Cost and Performance Optimization Practice Question
A SysOps administrator notices that the monthly bill for Amazon RDS is higher than expected. The environment includes multiple DB instances with low CPU and memory utilization. Which action will most effectively reduce costs while maintaining performance?
⚠ Common exam trap
The AWS exam often tests the misconception that deleting snapshots or changing storage type is the primary cost driver, when in reality, compute costs from over-provisioned instances are the largest contributor to RDS bills in low-utilization scenarios.
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
✓
Resize the DB instances to a smaller instance class
The DB instances have low CPU and memory utilization, indicating they are over-provisioned. Resizing to a smaller instance class directly reduces the hourly compute cost without affecting performance, as the current workload does not require the larger instance's capacity.
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 high availability
Why it's wrong here
Enabling Multi-AZ deployment creates a synchronous standby replica in a different Availability Zone, effectively doubling your database compute and storage costs while providing automatic failover. This is a high-availability feature, not a cost-optimization action, and it does nothing to address the low utilization of your existing DB instances. If your goal is to lower the monthly bill, adding a redundant replica would only increase costs further.
- ✓
Resize the DB instances to a smaller instance class
Why this is correct
Resizing the DB instances to a smaller instance class is the correct approach because it directly reduces the per-hour compute cost that scales with instance size. By analyzing Amazon CloudWatch metrics such as CPUUtilization, FreeableMemory, and DatabaseConnections, you can confirm the current instances are over-provisioned and select a smaller class that still satisfies your workload's peak demand. This right-sizing action lowers the compute component of the RDS bill immediately without sacrificing performance.
- ✗
Delete unused RDS snapshots
Why it's wrong here
Deleting unused RDS snapshots reduces snapshot storage charges, which are billed per GB-month on Amazon S3, but it does not affect the compute cost of the running DB instances. Since the problem is low utilization on the instances themselves, the main billing driver is the instance hours, not snapshot storage. While it's a valid housekeeping task, it won't meaningfully address the cost overrun described in the scenario.
- ✗
Provisioned IOPS (io1) storage for better performance
Why it's wrong here
Provisioned IOPS (io1) storage adds an additional per-IOPS charge on top of the allocated storage cost, and choosing this option would increase your monthly bill rather than decrease it. This storage type is intended for workloads with sustained I/O demands or performance requirements; if the current instances are underutilized and performance is adequate, provisioning more IOPS is unnecessary. It also does not reduce compute cost, so it is orthogonal to the goal of lowering overall spending.
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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.