A company is migrating five on-premises applications to VPCs in AWS. Each application is currently deployed in isolated on-premises virtual networks and should remain isolated in AWS. The applications must reach a shared services VPC, and all applications must be able to communicate with each other. If the migration succeeds, the company will repeat this for more than 100 applications. Which solution meets these requirements with the LEAST administrative overhead?

A transit gateway is the most scalable and administratively efficient solution. It allows you to connect all VPCs (application and shared services) to a central hub, simplifying routing and network management. As the number of applications grows to over 100, a transit gateway avoids the exponential increase in peering connections or VPN tunnels. Deploying software VPN tunnels or VPC peering connections directly between each application VPC and the shared services VPC would create a complex mesh network as the number of VPCs increases, leading to significant administrative overhead. Direct Connect is for connecting on-premises networks to AWS, not for inter-VPC communication within AWS.