DBS-C01 Workload-Specific Database Design Practice Question
A company is running an Oracle database on Amazon RDS. The database has a large table that is frequently accessed by multiple applications. The DBA notices that the table has a high number of index scans but the queries are still slow. Upon investigation, the buffer cache hit ratio is low. Which design change would BEST improve performance?
⚠ Common exam trap
A common mix-up: candidates choose a read replica (Option B) thinking it will distribute the load, but they fail to recognize that the low buffer cache hit ratio is a memory constraint on the primary instance, not a CPU or connection bottleneck, so offloading queries does not solve the underlying caching issue.
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
✓
Increase the instance size to provide more memory
The low buffer cache hit ratio indicates that the database's memory (buffer cache) is insufficient to cache frequently accessed data blocks, causing excessive physical I/O. Increasing the instance size provides more memory, which expands the buffer cache and allows more data to be cached, reducing disk reads and improving query performance. This directly addresses the root cause of the slow queries despite efficient index scans.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Convert the table to columnar storage using Amazon Redshift
Why it's wrong here
Redshift is a different service, not a design change within RDS.
- ✗
Add a read replica to offload queries
Why it's wrong here
Read replicas do not improve the primary instance's buffer cache.
- ✗
Migrate the table to Amazon DynamoDB with DAX
Why it's wrong here
Migrating to a different database type is a major change, not a simple design change.
- ✓
Increase the instance size to provide more memory
Why this is correct
More memory increases buffer cache capacity, reducing disk I/O.
Go deeper
Related to this question
About these practice questions
Courseiva writes every DBS-C01 question from scratch — 1,663 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
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.