A US company acquired a European company. The US team built a new microservices application that runs across five VPCs in the us-east-2 Region. The application must be able to access resources in a single VPC in the eu-west-1 Region and must not have access to any other VPCs. The VPC CIDR ranges in both Regions do not overlap. All AWS accounts are consolidated under one AWS Organizations organization. Which solution meets these requirements MOST cost-effectively?

The most cost-effective solution is to create an inter-region VPC peering connection from each of the five us-east-2 VPCs to the single eu-west-1 VPC. This directly connects the required VPCs without intermediate hops, incurring standard VPC peering data transfer costs. Creating a single transit gateway in eu-west-1 and attaching all VPCs would incur cross-region data processing charges for traffic from us-east-2 VPCs to the eu-west-1 Transit Gateway, making it more expensive. Creating a transit gateway in each region and peering them is a valid solution for complex, many-to-many connectivity but is overkill and more expensive for a simple five-to-one connection. It introduces additional Transit Gateway attachment and peering costs. A full-mesh configuration of VPC peering between all VPCs would involve unnecessary peering connections between the us-east-2 VPCs and is not supported for inter-region peering in a full mesh with the eu-west-1 VPC, making it overly complex and potentially more expensive or unfeasible.