The article you're responding to is exactly about Postgres. Here's Redis: https://fly.io/blog/last-mile-redis/

Here's a boring Rails app that uses Postgres: https://fly-global-rails.fly.dev/

And here's more Postgres:

https://fly.io/docs/getting-started/multi-region-databases/

https://fly.io/blog/globally-distributed-postgres/

Rails and websockets are not very good, Phoenix and websockets work great though.