This is reasonably common!
Latency will depend entirely on regions. In some cities we’re <1ms from AWS/GCP regions, in other’s it’s 20ms plus. We don’t have a good list of these so you’ll want to do some testing.
The best way to connect is to setup wireguard peers on the other end. We have a terraform example for doing this on AWS here: GitHub - fly-apps/rds-connector: Trivial Terraform example for a WireGuard peer to RDS