A company runs its website on EC2 instances in the us-east-1 Region and plans to deploy additional web servers in eu-central-1. The database must remain in us-east-1. After launching the eu-central-1 instances, those servers cannot reach the database in us-east-1. Which solution is the most operationally efficient way to restore connectivity?

VPC peering allows direct network routing between two VPCs using private IP addresses, making it the most operationally efficient solution for inter-region communication. To enable connectivity, the database security group's inbound rules must explicitly permit traffic from the private IP CIDR range of the eu-central-1 instances. Outbound rules on the database security group are for traffic originating from the database, not to it. While VPN connections can also link regions, VPC peering is generally preferred for its simplicity and direct routing within AWS, making it more operationally efficient for this use case. Adding a security group to outbound rules is incorrect because inbound rules control access to the database.