Setting up Rails 6 app with multiple databases on Heroku

Rails 6 is just around the corner. The release candidate two was recently released. This post is part of the Road to Rails 6 series which will prepare you for Rails 6.When we create a new brand new Rails 6 app, it is configured to use only one database. To start using multiple databases, we need to switch the database configuration from something called as two-tier configuration to three-tier configuration.