SOA-C02 Cost and Performance Optimization Practice Question
A company is running a stateful web application on a single EC2 instance with a 500 GB gp2 EBS volume. The instance is currently at 80% CPU and memory utilization during peak hours. The company wants to improve performance and scalability without incurring high costs. What should the SysOps administrator do?
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
✓
Implement an Application Load Balancer with an Auto Scaling group to distribute traffic across multiple instances.
Implementing an Application Load Balancer (ALB) with an Auto Scaling group allows the application to scale horizontally (scale out) based on demand. This improves both performance and scalability while optimizing costs because you only pay for the resources you use. Option B (vertical scaling) is incorrect because upgrading to a larger instance may require downtime and does not provide the same level of scalability; it also might be more costly. Option C (increasing swap space) is a temporary fix that does not address the root cause of high CPU and memory utilization; excessive swapping can degrade performance. Option D (migrating to gp3) improves I/O performance but does not help with CPU or memory constraints, and it does not enable scalability.
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 an Application Load Balancer with an Auto Scaling group to distribute traffic across multiple instances.
Why this is correct
An Application Load Balancer paired with an Auto Scaling group enables horizontal scaling: it distributes incoming traffic across multiple EC2 instances and automatically adjusts the fleet size based on demand. For stateful apps, ALB supports sticky sessions (session affinity) at the target group level, preserving user session data while still adding/removing instances. Because instances are added or removed dynamically, you pay only for the capacity you need, improving availability and cost efficiency.
- ✗
Upgrade the instance to a larger size (vertical scaling).
Why it's wrong here
Upgrading to a larger instance size is vertical scaling, which only lets you add CPU/RAM until you hit the largest available instance type. Changing the instance type usually requires stopping the instance, causing downtime on a single running host. It does not provide elasticity—you still overprovision for peak load and cannot scale back down automatically, making it both limited and costly.
- ✗
Increase the swap space on the instance to handle memory pressure.
Why it's wrong here
Increasing swap space turns disk into pseudo-memory, but disk I/O is orders of magnitude slower than RAM, so swap usage causes severe latency and can even hammer the EBS volume with additional I/O. It merely prevents out-of-memory kernel kills; it does not increase the instance's actual compute capacity or handle more concurrent requests. Under sustained memory pressure, the instance may thrash, degrading performance for all sessions rather than improving scalability.
- ✗
Migrate the EBS volume from gp2 to gp3 to improve I/O performance.
Why it's wrong here
Migrating the underlying EBS volume from gp2 to gp3 improves baseline throughput and IOPS (e.g., up to 3000 IOPS baseline), but that only relieves storage bottlenecks if the app is disk-bound. A web application under performance strain is usually constrained by CPU, memory, or connection concurrency, not raw disk speed. This change also leaves the single-instance architecture intact, so it does nothing for availability or horizontal scalability.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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