Which solution will meet these requirements?
Use AWS VPN CloudHub to connect the application VPC to all the other VPCs. Use a virtual private gateway to provide traffic flow between all the VPCs.
Create VPC peering connections between the application VPC and all the other VPCs. Update the security groups and route tables to allow traffic flow between all the VPCs.
Create a transit gateway in the application account. Attach the application VPC and all the other VPCs to the transit gateway. Create a transit gateway route table to direct traffic between the VPCs.
Share the application VPC with the other AWS accounts by using AWS Resource Access Manager (AWS RAM). Deploy the microservices in the shared VPC.
Explanations:
AWS VPN CloudHub is primarily for connecting remote sites via VPN. It does not provide the scalability and simplicity needed for inter-VPC communication in a multi-account setup. Managing multiple VPN connections would increase operational overhead.
VPC peering can be used for connecting VPCs, but it does not scale well as the number of VPCs increases. Each VPC can only have a limited number of peer connections, and managing routes and security across multiple peered VPCs can become complex and cumbersome.
Creating a transit gateway simplifies interconnectivity between multiple VPCs, allowing for efficient routing and management. It supports a scalable architecture, reduces operational overhead, and enables the application to communicate privately with microservices across different accounts without needing to establish multiple peering connections.
Sharing a VPC using AWS RAM could complicate resource management and security. This approach also limits the isolation and independence of accounts, which goes against best practices for multi-account architecture in AWS.
I believe the answer is:
Create a transit gateway in the application account. Attach the application VPC and all the other VPCs to the transit gateway. Create a transit gateway route table to direct traffic between the VPCs.