Not sure what they mean by "json gem", as it comes with ruby and not installed via gem install command.
I've always used
require 'json/ext'
This uses the C extension version and is much faster.
I've always used
require 'json/ext'
This uses the C extension version and is much faster.
Meaning Ruby ships with that gem pre-installed, but it's still a gem and you can upgrade/downgrade it in your gemfile if you so chose.
As for `require "json/ext"` that's outdated knowledge.