A solutions architect is creating an application.

Understanding the Requirement: The application running on EC2 instances in private subnets needs frequent access to large confidential files stored in S3, minimizing data transfer costs.

Analysis of Options:

Gateway Endpoint for S3: Provides a secure, scalable, and cost-effective way for instances in private subnets to access S3 without using the internet or NAT gateways, thus minimizing data transfer costs.

Single NAT Gateway: Incurs additional costs for data transfer through the NAT gateway, which is not cost-effective.

PrivateLink Interface Endpoint for S3: Primarily used for accessing AWS services over a private connection but is more complex and costly compared to a gateway endpoint for S3.

Multiple NAT Gateways: Increases costs significantly and adds complexity without offering the cost benefits of a gateway endpoint.

Best Solution:

Gateway Endpoint for S3: This solution provides the required access with the least data transfer costs and minimal complexity.