> Also, you would want to take care because in this situation, you're exposing port 5432 to the world as well.
> [...] You could do something like 127.0.0.1:5432:5432

Yeah with Kamal 2 you can avoid exposing the port to the world by setting the postgres accessory `port` to `127.0.0.1:5432:5432` instead of `5432:5432`, and in the `database.yml` or env var config making sure the host is `servicename-accessoryname` instead of an IP, e.g. `app1-postgres`, so the Rails app can connect to the database via Kamal 2's internal docker local network.

This is explained in the the Kamal 2 presentation video at 14:26: https://youtu.be/QC4b2teG_hc?feature=shared&t=866. It is not yet well known as this tip was documented in deploy.yml only last week in the Rails main branch, but if you run `rails new --main` you will see those deploy.yml comments about the local network.

But as David said, that will only work for single server setups.