I think category theory can be at its most useful when used as part of the day-to-day routine of development. I don’t think it’s only limited to working in large teams, but large projects and large teams are very different. Even working on your own, category theory is really so handy.For me, it is like a lens to look at the world, and particularly the world of functional programming software projects. It’s like a set of train tracks, or a snap-to-grid button in a piece of software. It allows you to think about problems spatially, in the physical world, write less code and identify discrepancies in your mental model of the problem domain early. By forcing oneself to use a limited set of simple rules, it supercharges code reuse and reduces codebase size, thereby increasing maintainability.