Implementing Auto Scaling with a mix of On-Demand and Spot Instances best meets the company's need for a solution that adapts to variable loads while optimizing costs. Auto Scaling allows the application to handle unpredictable surges in traffic by automatically adjusting the amount of compute capacity, known as horizontal scaling. Using a mix of On-Demand and Spot Instances leverages cost savings from the Spot Market while maintaining the reliability of On-Demand Instances. A single EC2 instance adjusted for peak traffic does not efficiently handle variable loads as it would lead to overprovisioning during low-traffic periods. Vertical scaling can be effective for predictable workloads but is less flexible and can lead to downtime during scaling operations. Using an Application Load Balancer without Auto Scaling does not address the requirement for the compute layer to adapt to changing demands.