A company is running a workload in the AWS Cloud.

The AWS best practice that ensures the most cost-effective architecture for the workload is rightsizing. Rightsizing means selecting the most appropriate instance type or resourceconfiguration that matches the needs of the workload. Rightsizing can help optimize performance and reduce costs by avoiding over-provisioning or under-provisioning of resources1. Loose coupling, caching, and redundancy are other AWS best practices that can improve the scalability, availability, and performance of the workload, but they do not necessarily ensure the most cost-effective architecture.