There are some cases where you might want to implement a validation method for your Sequelize model that queries other rows in your database to check business rules.
Recently I had the opportunity to use Ruby on Rails to develop an internal system for the company I work. It was a good exercise to remember how productive this framework can be, and how single page applications are not always the best choice for every problem.
I was beating my brain out today trying to figure out why my error handling middleware wasn't being called inside the project test suite, but it worked when I did the request directly through the browser.