AWS Certified Solutions Architect – Professional — Question 886

A company has an Amazon EC2 deployment that has the following architecture:
✑ An application tier that contains 8 m4.xlarge instances
✑ A Classic Load Balancer
✑ Amazon S3 as a persistent data store
After one of the EC2 instances fails, users report very slow processing of their requests. A Solutions Architect must recommend design changes to maximize system reliability. The solution must minimize costs.
What should the Solutions Architect recommend?

Answer options

• A. Migrate the existing EC2 instances to a serverless deployment using AWS Lambda functions
• B. Change the Classic Load Balancer to an Application Load Balancer
• C. Replace the application tier with m4.large instances in an Auto Scaling group
• D. Replace the application tier with 4 m4.2xlarge instances

Correct answer: C

Explanation

Replacing the fixed fleet of instances with an Auto Scaling group using smaller m4.large instances ensures high availability and automatic recovery of failed instances, which directly addresses the reliability issue. This approach minimizes costs because the Auto Scaling group can dynamically scale in and out based on demand, rather than maintaining a static number of oversized instances. Other options, such as using fewer but larger instances (m4.2xlarge) or just changing the load balancer, do not provide the necessary automatic self-healing and cost optimization.