A company wants to refactor its retail ordering web application that currently has a load-balanced Amazon EC2 instance fleet for web hosting, database API services, and business logic. The company…

While S3, API Gateway, and Lambda are good for serverless, the option incorrectly uses SQS for 'database API services'; SQS is a messaging queue, not an API service.

AWS Elastic Beanstalk involves managing underlying EC2 instances, which is not as decoupled or cost-optimized as a fully serverless approach for web hosting and increases operational overhead.

This solution uses Amazon S3 for highly scalable and cost-effective static web hosting. AWS AppSync provides a scalable, real-time GraphQL API for database services, decoupling the front end from the backend. AWS Lambda processes business logic in a serverless, pay-per-execution model, minimizing compute costs. Amazon SQS acts as a highly available, scalable queue to store order requests, providing a mechanism to retain failed orders for later processing and ensuring reliability in a decoupled manner.

Amazon Lightsail is a simplified, fixed-price solution that may not provide the full flexibility, scalability, and cost optimization capabilities required for a highly decoupled retail application, compared to dedicated serverless services.