A subnet using mask 255.255.255.240 is out of free IPs. You need 10 more IPs and all existing and new VMs must reach each other without extra routes. What should you do?

Expanding the subnet's IP range using gcloud is the correct solution because it directly addresses the need for more IPs within the existing subnet, preserving connectivity. This operation modifies the CIDR block of the current subnet, adding more available IP addresses without changing its identity. Deleting and recreating the subnet would cause downtime and require reconfiguring existing VMs. Creating a new project with Shared VPC is an overly complex solution for simply adding IPs and doesn't directly solve the subnet IP exhaustion. Creating a new subnet with the same starting IP and a wider range is not possible; subnet CIDR blocks cannot overlap within the same VPC network, and you cannot "overwrite" an existing subnet this way.