At the bottom of the article they have "methodology" link, which explains how the test was performed and how you can replicate the tests yourself. https://ninefold.com/performance-method/

There's still nothing there about making your Rails apps perform better. That link just shows how to create an app on Heroku and hit it with flood.io traffic.

That's methodology for the tests, not methodology for mailing a Rails app perform better.

Agreed. Might be an interesting service to check out, but the title is extremely misleading.