I've had it work well with two environments. On the same host, different ports. Then have ngnix rout to the active port, and have a second Dns that nginx routes

I've had it work well with two environments. On the same host, different ports. Then have ngnix rout to the active port, and have a second Dns that nginx routes to the inactive one. Push to the inactive one, verify, swap the ninx config. Migrations are forward/backward compatible and can be applied whenever. This is really the only tricky part. Static content on CDN with different urls(hash in name or folder per deploy)