There are foundational problems that can be studied via category theory, such as the view-update problem [1]. So, if you want to design a database you are faced

There are foundational problems that can be studied via category theory, such as the view-update problem [1]. So, if you want to design a database you are faced with the problem of two users trying to update the same data at the same time and you will have to make a design decision about how it should work. I don't know if the video itself maybe fails to properly point out uses of category theory. My opinion on the matter is that if you do want to use mathematics in your everyday work, the main applications will come from the mathematics you know the best. So, whether you are interested in category theory or not will also influence whether you use it. Many of the concepts in category theory can be done instead in algebra and analysis, but it is the spirit of unification that inspires people to study category theory. A lot of functional programmers are delighted when they learn about axioms such as associativity (since you can prove thing about your program) but the concept is much older than category theory. So you can just know associativity if you are not really interested in category theory and that will already take you far. [1] M. Johnson and R. Rosebrugh, Fibrations and universal view updatability, Theoretical Computer Science 388.1, 2007, 109–129.