AWS Certified Solutions Architect – Associate (SAA-C02) — Question 663

A company hosts a website analytics application on a single Amazon EC2 On-Demand Instance. The analytics software is written in PHP and uses a MySQL database. The analytics software, the web server that provides PHP, and the database server are all hosted on the EC2 instance. 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. Migrate the database to an Amazon RDS for MySQL DB instance. Create an 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 to each EC2 instance.
• B. Migrate the database to an Amazon RDS for MySQL DB instance. Create an 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. Migrate the database to an Amazon Aurora MySQL DB instance. 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 surpasses 75%.
• D. Migrate the database to an Amazon Aurora MySQL DB instance. Create an AMI of the web application. Apply the AMI to launch template. Create an Auto Scaling group with 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 scalable solution because migrating the database to Amazon Aurora MySQL offloads the database tier, while using an Auto Scaling group with a Spot Fleet allows the web tier to scale dynamically and cheaply during peak hours. Options A and B rely on a static, manually configured second On-Demand instance which is not cost-optimal and does not scale seamlessly. Option C is incorrect because stopping the EC2 instance to change its type causes application downtime, which is not a seamless scaling solution.