The correct action is to create a Read Replica in the same region. This offloads read traffic from the primary MySQL RDS instance, directly addressing the 80% CPU utilization during peak hours by distributing SELECT queries to the replica, which asynchronously replicates data using MySQL’s native binlog-based replication. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of how Read Replicas reduce primary instance load without requiring a larger instance size or a Multi-AZ deployment—a common trap is confusing Multi-AZ (which provides high availability, not read scaling) with Read Replicas. The key distinction is that Read Replicas improve read performance by handling read-heavy workloads, while the primary focuses on writes. For the exam, remember the mnemonic: “Read Replicas for reads, Multi-AZ for needs”—meaning use replicas to scale reads and Multi-AZ only for failover, not performance.
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.
Network Topology
Refer to the exhibit. An application team notices that the MySQL RDS instance 'mydb' is running at 80% CPU utilization during peak hours. They need to improve read performance without increasing the CPU load on the primary instance. Which action should they take?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a Read Replica in the same region
Creating a Read Replica offloads read traffic from the primary MySQL RDS instance, reducing CPU load on the primary while improving read performance for applications. Read Replicas asynchronously replicate data using MySQL’s native binlog-based replication, allowing the primary to focus on write operations without additional CPU overhead from serving reads.
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.
✗
Increase the DB instance class to db.r5.xlarge
Why it's wrong here
Scales vertically but does not offload reads; still single point of load.
✓
Create a Read Replica in the same region
Why this is correct
Read Replica offloads read queries, reducing CPU on primary.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change storage type to io1 with higher IOPS
Why it's wrong here
Storage change does not reduce CPU utilization.
✗
Enable Multi-AZ deployment
Why it's wrong here
Multi-AZ provides high availability, not read scaling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing Multi-AZ (which provides failover but no read scaling) with Read Replicas (which offload reads), leading candidates to select Multi-AZ when the goal is to reduce CPU load on the primary.
Detailed technical explanation
How to think about this question
MySQL Read Replicas use asynchronous replication based on binary log (binlog) position or Global Transaction Identifiers (GTIDs), with a default replication lag of typically under 100 ms in the same region. In production, you can create up to 15 Read Replicas per primary, and they can be promoted to standalone instances for disaster recovery, but they do not support write operations unless promoted.
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: Create a Read Replica in the same region — Creating a Read Replica offloads read traffic from the primary MySQL RDS instance, reducing CPU load on the primary while improving read performance for applications. Read Replicas asynchronously replicate data using MySQL’s native binlog-based replication, allowing the primary to focus on write operations without additional CPU overhead from serving reads.
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.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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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