Rails applications that are successful often end up with users from all parts of the world. Learn how to make them fast and responsive for everybody on the planet.
The fly-ruby gem provides a basic toolkit for making Rails applications across multiple regions. Read Run Ordinary Rails Apps Globally to see how the gem can be used in a Rails application to make it work across multiple regions.
Since many Rails applications depend on Redis for caching, background workers, and Action Cable, it's important to think through deploying Redis globally.
Postgres also requires consideration for global deployments.