The answer is to add a read replica. This action most effectively improves performance and reduces cost for a read-heavy RDS for MySQL instance because it offloads SELECT queries from the primary database, directly alleviating high CPU utilization during business hours. By distributing read traffic to a replica, you can keep the primary instance smaller and only pay for replica resources when needed, avoiding the expense of scaling up the entire instance. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of RDS read replicas as a targeted scaling strategy for read-heavy workloads, often appearing as a distractor against scaling vertically or using Multi-AZ. A common trap is confusing Multi-AZ (for high availability) with read replicas (for performance and cost optimization). Memory tip: think “read replica, read relief”—if the bottleneck is reads, replicate to distribute.
SOA-C02 Cost and Performance Optimization Practice Question
This SOA-C02 practice question tests your understanding of cost and performance optimization. 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 SysOps administrator manages an Amazon RDS for MySQL instance that experiences high CPU utilization during business hours. The application is read-heavy. Which action will most effectively improve performance and reduce cost?
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.
Adding a read replica offloads read traffic from the primary RDS for MySQL instance, directly addressing the read-heavy workload and high CPU utilization. This improves performance by distributing SELECT queries to the replica, and reduces cost because you can use a smaller primary instance and only pay for the replica's resources when needed, rather than scaling up the entire instance.
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.
✗
Enable Multi-AZ deployment.
Why it's wrong here
Incorrect. Multi-AZ provides high availability and failover, but does not reduce CPU utilization on the primary instance.
✗
Scale up the instance size to a larger instance class.
Why it's wrong here
Incorrect. Scaling up increases performance but also increases cost, and does not optimize cost.
✓
Add a read replica.
Why this is correct
Correct. Read replicas handle read traffic, reducing load on the primary instance and improving performance cost-effectively.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable automated backups.
Why it's wrong here
Incorrect. Automated backups enable point-in-time recovery but do not reduce CPU usage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Multi-AZ (which is for high availability) with read replicas (which are for read scaling), and assume that any scaling must involve resizing the instance rather than adding a separate read-only endpoint.
Detailed technical explanation
How to think about this question
Amazon RDS read replicas use asynchronous replication based on MySQL's native binlog replication, with a replication lag typically under a second in the same region. The read replica can be promoted to a standalone instance if needed, and you can create multiple replicas to scale read-heavy workloads horizontally. In a real-world scenario, you might also use a read replica for reporting or analytics without impacting the production workload.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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.
Cost and Performance Optimization — This question tests Cost and Performance Optimization — 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. — Adding a read replica offloads read traffic from the primary RDS for MySQL instance, directly addressing the read-heavy workload and high CPU utilization. This improves performance by distributing SELECT queries to the replica, and reduces cost because you can use a smaller primary instance and only pay for the replica's resources when needed, rather than scaling up the entire instance.
What should I do if I get this SOA-C02 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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A SysOps administrator notices that an Amazon RDS for MySQL instance has high read activity. The application performs many read queries but few writes. The database is currently a single db.r5.large instance. What change would improve read performance and reduce cost?
medium
A.Enable Multi-AZ for high availability and use the standby for reads.
B.Increase the instance size to db.r5.xlarge.
C.Migrate the database to Amazon DynamoDB.
✓ D.Create a read replica and use a smaller instance type for the replica.
Why D: Adding a read replica distributes read traffic, improving performance, and using a smaller instance type for the replica reduces cost. Option A is wrong because vertical scaling increases cost. Option B is wrong because Multi-AZ does not offload reads. Option D is wrong because moving to DynamoDB may not be compatible with the application.
Variation 2. A SysOps administrator is troubleshooting high CPU utilization on an RDS for MySQL instance. The application is read-heavy. Which optimization technique would improve performance and potentially reduce costs?
hard
A.Delete unused indexes from the database.
✓ B.Implement RDS Read Replicas to offload read traffic.
C.Increase the allocated storage size.
D.Enable Multi-AZ deployment for failover support.
Why B: Option A is correct because adding Read Replicas offloads read queries, reducing CPU on the primary and allowing use of smaller instance types. Option B is wrong because Multi-AZ is for high availability, not performance. Option C is wrong because increasing storage doesn't improve CPU. Option D is wrong because deleting unused indexes reduces storage but not CPU.
Variation 3. An application uses an RDS MySQL DB instance. The administrator notices that read performance is poor during peak hours. What is a cost-effective way to improve read performance?
medium
A.Use Amazon ElastiCache for caching.
B.Enable Multi-AZ deployment.
C.Scale up the DB instance to a larger size.
✓ D.Create a read replica in the same region.
Why D: Option B is correct because read replicas offload read traffic from the primary instance. Scaling up is more expensive. Multi-AZ is for high availability, not read performance. Using ElastiCache adds complexity and cost.
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Question Discussion
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