[gkop]

At the very beginning, Rails made a big deal about aspiring to database agnosticism, and to this day ActiveRecord supports a number of SQL databases out of the box.

The backend for ActiveSupport::Cache::Store is similarly interchangeable (memcached, disk, etc.)

I can see why adding a Redis dependency makes opinionated programmers grumpy, and I predict ActionCable supports other backends than Redis eventually.