An ecommerce company is running a seasonal online sale. The website runs on Amazon EC2 instances across multiple Availability Zones and must handle sudden traffic spikes during the sale. Which solution will meet these requirements MOST cost-effectively?

An Auto Scaling group configured to scale out as traffic increases, combined with a launch template using a preconfigured AMI, is the most cost-effective solution. This setup automatically adjusts capacity to meet demand, preventing over-provisioning during low traffic and ensuring availability during spikes. The launch template with a preconfigured AMI ensures new instances are ready quickly. Incorrect options: Stopping half of an Auto Scaling group's instances and using them for scale-out is not a standard or efficient Auto Scaling configuration and may lead to performance issues or delays. Setting a high minimum size for the Auto Scaling group to handle peak load without scaling out is not cost-effective, as it keeps unnecessary instances running during off-peak hours. While CloudFront and ElastiCache improve performance, the proposed Auto Scaling strategy of scaling in after cache population doesn't address the primary need for dynamic scaling to handle ongoing traffic spikes cost-effectively.