AWS Certified Cloud Practitioner — Question 321

An ecommerce company has Amazon EC2 instances running as web servers. There is a predictable pattern of peak traffic load that occurs two times each day, always at the same time. The EC2 instances are idle for the remainder of the day.

What is the MOST cost-effective way to manage these resources while maintaining fault tolerance?

Answer options

• A. Use an Auto Scaling group to scale resources in and out based on demand.
• B. Purchase Reserved Instances to ensure peak capacity at all times.
• C. Write a cron job to stop the EC2 instances when the traffic demand is low.
• D. Write a script to vertically scale the EC2 instances during peak traffic demand.

Correct answer: A

Explanation

Using an Auto Scaling group allows the company to automatically scale out during predictable peak hours and scale in during idle times, optimizing costs while ensuring high availability. Purchasing Reserved Instances for peak capacity at all times is wasteful because the resources sit idle for most of the day. Running custom scripts for stopping instances or scaling vertically introduces operational complexity and risk of downtime, failing to provide robust fault tolerance.