A company provides an API that automates tax computations based on item prices. During the holiday season the number of requests spikes and response times slow. A solutions architect must design a scalable, elastic solution. What should the architect implement?

This solution leverages AWS Lambda, a serverless compute service, which automatically scales to handle spikes in requests without requiring manual intervention or pre-provisioning. API Gateway provides a fully managed, scalable entry point for the API. This combination is highly elastic and cost-effective, as you only pay for the compute time consumed. Hosting the API on a single EC2 instance (option 1) or behind an ALB with two EC2 instances (option 3) would require manual scaling or auto-scaling group configuration, which is less elastic and more complex than Lambda for this use case. Using API Gateway with an EC2 instance (option 4) still relies on the EC2 instance for computation, negating the serverless benefits of Lambda for elasticity and scalability.