Decoupling Monolithic App with Auto Scaling and RDS Read Replicas
Short answer
A Resize the EC2 instance, configure an Auto Scaling group, and add an RDS read replica for read requests.
Question
Key Takeaways
The core trap is confusing read-only replicas with write-capable databases; correct scaling requires separating read traffic from the primary instance while enabling horizontal compute scaling.
This question addresses how to resolve high CPU utilization and read performance bottlenecks in a monolithic AWS application using Auto Scaling and RDS Read Replicas.
Common mistake: Option B is a common wrong answer because it suggests redirecting all traffic (including writes) to the replica, which violates the read-only nature of RDS replicas.
Expert Analysis
Why the Answer Is Correct
Option A correctly implements two distinct architectural improvements: horizontal scaling for the compute layer and offloading read traffic for the database. By configuring an Auto Scaling group (even with min/max=1 initially, it establishes the pattern for elasticity), the EC2 capacity can grow during peak loads, directly addressing high CPU utilization. Simultaneously, adding an RDS Read Replica allows the application to direct read requests away from the primary instance, resolving the degraded read performance without impacting write operations.
Why the Other Options Are Wrong
Option B fails because RDS Read Replicas are strictly for read-only operations; redirecting write traffic to them will cause errors or data inconsistency. Option C only adds a second EC2 instance but does not address the RDS read bottleneck, leaving the database as a single point of failure for reads. Option D merely increases instance sizes (vertical scaling) which is cost-inefficient and does not provide the fault tolerance or elastic scalability inherent in distributed architectures like Auto Scaling groups.
Community Comment Notes
Community feedback strongly supports Option A. One user noted that Option B is incorrect because 'RDS read replicas are designed to handle read operations only'. Another commenter highlighted that Option A effectively addresses both the CPU and read performance issues simultaneously. While some users questioned the utility of an Auto Scaling group with min=max=1, this is often used in exam scenarios to indicate the capability or configuration intent rather than immediate active scaling.
Exam Strategy
Always distinguish between vertical scaling (changing instance size) and horizontal scaling (adding instances via Auto Scaling). When asked to improve read performance specifically, look for 'Read Replica' solutions, and ensure you never send write traffic to a read-only replica.
Frequently Asked Questions
Why is an Auto Scaling group with min=max=1 valid?
Can I send write traffic to an RDS Read Replica?
Community Votes
100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 4 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 4
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ltetti 👍 4 Answered AOption B incorrectly suggests redirecting all read/write traffic to the replica. RDS read replicas are designed to handle read operations only, not write operations. Writes must still be handled by the primary DB instance
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dhewa 👍 2 Answered AThis approach addresses both the high CPU utilization on the EC2 instance and the degraded read performance on the RDS instance effectively.
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GOTJ 👍 2 Answered AOption "A", but... How does an auto scaling group with min = max = 1 instances contribute to the solution?
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Abbas_Abi_AWS 👍 2 Answered AA is correct
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