Push a Rails app and Railpack installs your gems, precompiles the assets and starts it, on a server you own.
Deplo builds with Railpack by default, so a Rails project needs no Dockerfile to get started.
Short answers to what comes up before moving a Rails app onto your own server.
Yes. Managed databases live in the same environment and reach the app over the internal network.
In the app's settings, per environment. They are available during the build too, and secret values are write only: nothing reads them back.
No. The new container has to pass its health check before the old one is retired.
Answer three questions and pick a host, or install Deplo on a server you already have. It's free, and leaving is as easy as arriving. What you do with the money you save is your business.