DBS-C01 Monitoring and Troubleshooting Practice Question
A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. During the migration, the database administrator notices that the CPU utilization on the RDS instance is consistently above 90% during peak hours, even though the on-premises server had similar specifications. The application queries are mostly SELECT statements with occasional DML. The RDS instance is db.r5.large with 500 GB of General Purpose SSD (gp2) storage. Which change would most likely reduce CPU utilization?
⚠ Common exam trap
AWS often tests the misconception that increasing storage or adding a read replica can solve CPU bottlenecks, but the correct answer requires recognizing that CPU saturation is a compute issue best addressed by scaling instance size.
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
✓
Upgrade to a larger instance type, such as db.r5.xlarge.
The db.r5.large instance type has 2 vCPUs and 16 GiB of memory. Sustained CPU utilization above 90% during peak hours indicates that the instance is compute-bound for the workload. Upgrading to db.r5.xlarge (4 vCPUs, 32 GiB memory) doubles the available CPU capacity, directly reducing CPU utilization for the same query load. The on-premises server had similar specifications, but RDS instances may have different CPU architectures or hypervisor overhead, making the larger instance the most direct fix.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a read replica and redirect all SELECT queries to the replica.
Why it's wrong here
While this reduces read load, the primary still handles writes and some reads; CPU may remain high if the bottleneck is not solely reads.
- ✗
Enable Multi-AZ to offload CPU to the standby instance.
Why it's wrong here
Multi-AZ does not offload CPU; the standby is not used for queries unless a failover occurs.
- ✗
Increase the allocated storage to 1 TB to improve I/O performance.
Why it's wrong here
Increasing storage does not improve CPU capacity.
- ✓
Upgrade to a larger instance type, such as db.r5.xlarge.
Why this is correct
A larger instance provides more CPU cores and better performance, directly addressing high CPU utilization.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DBS-C01 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 DBS-C01 exam.