A company is extending a secure on-premises network to AWS using AWS Direct Connect. The on-premises network has no direct internet access. An on-premises application needs to access an Amazon S3 bucket. Which solution meets these requirements MOST cost-effectively?

The most cost-effective solution is to use a VPC and an Amazon S3 interface endpoint. An S3 interface endpoint (powered by AWS PrivateLink) allows private connectivity from your VPC to S3, without requiring traffic to traverse the public internet. When combined with Direct Connect, this means your on-premises application can access S3 securely and privately over the Direct Connect connection, bypassing internet gateways and NAT gateways. Creating a public VIF would send S3 traffic over the public internet, which is less secure and less private than using an interface endpoint. Creating a NAT gateway would incur additional costs for the gateway and data processing, and is typically used for outbound internet access from a VPC, not for private access to AWS services from on-premises. VPC peering is used to connect two VPCs, not to connect an on-premises network directly to an S3 endpoint.