Connect to (Private) RDS from Nextjs on vercel

It looks like you would need to take out an Enterprise Plan to use Secure Compute with Vercel.

They look like they are hosted on AWS and there for you have 2 options..

1. Setup a Site to Site VPN with your VPC so that your Front end can connect to your RDS privately.
2. Use VPC Peering to peer your Front end VPC with your BackEnd RDS instance VPC

https://vercel.com/docs/security/secure-compute#vpc-or-vpn-support