DBS-C01 Workload-Specific Database Design Practice Question
A gaming company uses Amazon RDS for PostgreSQL to store player profiles and game state. They report slow queries during peak hours. The DB instance is a db.r5.2xlarge with 500 GB gp2 storage. Which design change would MOST improve read performance for the most frequently accessed player profiles?
⚠ Common exam trap
Watch out — candidates often confuse increasing instance size (Option C) or IOPS (Option B) as the only way to fix slow queries, when the real solution is to offload read traffic to a read replica, which is a common AWS exam pattern for read-heavy workloads on RDS.
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
✓
Add a read replica in the same AZ
Adding a read replica in the same Availability Zone (AZ) offloads read traffic from the primary RDS for PostgreSQL instance, directly improving read performance for frequently accessed player profiles during peak hours. Read replicas asynchronously replicate data using PostgreSQL's streaming replication and can serve SELECT queries without impacting the primary instance's write workload or connection limits.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Implement application-level sharding by player ID
Why it's wrong here
Application-level sharding by player ID does not address the read performance bottleneck on a single RDS instance; it distributes write load and storage across multiple databases but does not reduce query latency on the existing db.r5.2xlarge with gp2 storage, where the issue is I/O throughput or caching capacity for frequently accessed profiles. This option is tempting because sharding is a common horizontal scaling technique for high-write workloads or when a single database cannot handle total data volume, and it would be correct if the problem were write contention or storage capacity exhaustion rather than read-heavy profile lookups during peak hours.
- ✗
Increase provisioned IOPS on the existing volume
Why it's wrong here
Increasing IOPS improves write throughput, but does not directly offload read queries.
- ✗
Upgrade to a db.r5.4xlarge instance
Why it's wrong here
Vertical scaling helps, but read replicas are more cost-effective for read-heavy workloads.
- ✓
Add a read replica in the same AZ
Why this is correct
Read replicas offload read traffic from the primary, improving performance for read-heavy workloads.
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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.