DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
Sharding is complex and may not be necessary; read replicas are simpler.
✗
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.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates 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.
Detailed technical explanation
How to think about this question
Amazon RDS read replicas use PostgreSQL's native streaming replication over TCP port 5432, maintaining an asynchronous copy that can lag by seconds under heavy write load. In the same AZ, network latency is minimized (<1 ms), and read replicas can be promoted to standalone instances if needed, but they do not support write operations. For frequently accessed player profiles, enabling read replica automatic scaling or using a Multi-AZ deployment with a standby (which is not used for reads) would not help; a dedicated read replica is the correct pattern for read scaling.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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