A company has two AWS accounts, Account A and Account B. Each account has a VPC. An application in the VPC in Account A must write to an Amazon S3 bucket in Account B. The application in Account A already has permission to write to the bucket. Both the application and the S3 bucket are in the same AWS Region. The company must not send traffic over the public internet. Which solution meets these requirements?

The correct solution is to create a gateway VPC endpoint for Amazon S3 in Account A and update its VPC route table. A gateway VPC endpoint provides private connectivity from your VPC to S3 without traversing the public internet, directly addressing the requirement to avoid public internet traffic. Since the application is in Account A and needs to access an S3 bucket (regardless of which account it's in, as long as permissions are granted), the endpoint should be in Account A. Creating a transit gateway in each account with VPC attachments is overly complex and unnecessary for this specific S3 access requirement. Deploying a software VPN appliance and creating a VPN connection is also an overly complex and less performant solution compared to a VPC endpoint for S3. Creating a VPC peering connection between the VPCs would allow direct network communication between the VPCs, but S3 is a public service accessed via endpoints, not directly via private IP addresses within a peered VPC. While peering could facilitate other cross-account communication, it doesn't directly solve the private S3 access problem as efficiently as a gateway endpoint.