EC2 instances in private subnets must initiate all outbound requests, including traffic to the on-premises datacenter over Direct Connect. No external resource must initiate connections to these EC2 instances. The on-premises customer gateway uses a stateful firewall that filters traffic for multiple VPCs, and the company prefers to use a single IP match on the firewall to allow all EC2 traffic. Which option meets the requirements with the least operational overhead?

The correct option is to deploy a private NAT Gateway. This allows EC2 instances in private subnets to initiate outbound connections to the on-premises datacenter via Direct Connect. The private NAT Gateway provides a single, static IP address that can be configured on the on-premises firewall, meeting the requirement for a single IP match. This approach ensures that no external resources can initiate connections to the EC2 instances, as the NAT Gateway only handles outbound-initiated traffic. It offers high availability and managed service benefits, leading to the least operational overhead. Creating a VPN over Direct Connect or configuring the on-premises firewall to filter requests directly from the on-premises network to EC2 instances would not provide a single source IP for all outbound traffic from the EC2 instances, making firewall management more complex. Deploying a NAT instance would require more operational overhead for management and scaling compared to a managed NAT Gateway.