AWS Certified Solutions Architect – Associate (SAA-C03) — Question 954

A company hosts a website analytics application on a single Amazon EC2 On-Demand Instance. The analytics application is highly resilient and is designed to run in stateless mode.

The company notices that the application is showing signs of performance degradation during busy times and is presenting 5xx errors. The company needs to make the application scale seamlessly.

Which solution will meet these requirements MOST cost-effectively?

Answer options

• A. Create an Amazon Machine Image (AMI) of the web application. Use the AMI to launch a second EC2 On-Demand Instance. Use an Application Load Balancer to distribute the load across the two EC2 instances.
• B. Create an Amazon Machine Image (AMI) of the web application. Use the AMI to launch a second EC2 On-Demand Instance. Use Amazon Route 53 weighted routing to distribute the load across the two EC2 instances.
• C. Create an AWS Lambda function to stop the EC2 instance and change the instance type. Create an Amazon CloudWatch alarm to invoke the Lambda function when CPU utilization is more than 75%.
• D. Create an Amazon Machine Image (AMI) of the web application. Apply the AMI to a launch template. Create an Auto Scaling group that includes the launch template. Configure the launch template to use a Spot Fleet. Attach an Application Load Balancer to the Auto Scaling group.

Correct answer: D

Explanation

Option D is the most cost-effective and seamless solution because stateless, highly resilient applications are ideal candidates for Spot Instances, which offer up to a 90% discount compared to On-Demand pricing. Utilizing an Auto Scaling group with an Application Load Balancer allows the application to automatically scale in and out based on traffic demands without manual intervention. In contrast, Options A and B rely on more expensive On-Demand instances without dynamic scaling, and Option C causes application downtime by stopping the instance to scale vertically.