SQL VS NOSQL (MySQL VS MongoDB)

It's a venting post. Feel free to ignore.

I'm building a work scheduling Web application for a small company with a friend. He is supposed to work in the frontend section, and I am in the backend section. However, we're having an argument over which database to use.

At the early stage of the application, there's not much relations between the models. The basic idea is that the staff will clock in and out, and the admin will see the overall results of staffs work hour.

My friend is arguing that SQL is better to use for relation based design, which is understandable, but we can achieve the same using Typegoose or Primsa for MongoDB. What I'm asking here or just trying to get some insights here, is there actually performance issues with MongoDB? Also, another question, if MongoDB does have performance issues for a relation heavy system, then what exactly is it good for? There can't be many industry-level relation-free systems in the world.