Your company and one of its partners each have a Google Cloud project in separate organizations. Your company's project (prj-a) runs in Virtual Private Cloud (vpc-a). The partner's project (prj-b) runs in vpc-b. There are two instances running on vpc-a and one instance running on vpc-b. Subnets defined in both VPCs are not overlapping. You need to ensure that all instances communicate with each other via internal IPs, minimizing latency and maximizing throughput. What should you do?

VPC Network Peering allows internal IP connectivity between two Virtual Private Cloud (VPC) networks, even if they belong to different Google Cloud projects and organizations. This directly addresses the requirement for instances in vpc-a and vpc-b to communicate using internal IPs, offering high throughput and low latency as traffic stays within Google's network. Setting up a VPN between VPCs using Cloud VPN would provide connectivity, but it introduces encryption overhead and typically has higher latency and lower throughput compared to VPC Network Peering, making it less ideal for minimizing latency and maximizing throughput between Google Cloud VPCs. Configuring IAP TCP forwarding is for secure SSH/RDP access to instances from outside the VPC without public IPs, not for direct instance-to-instance communication via internal IPs across different VPCs. Creating additional instances and installing OpenVPN is a manual, software-defined VPN solution that would be more complex to set up, manage, and would likely offer lower performance than native Cloud VPN or VPC Network Peering.