When building applications, one of the most important design principles to keep in mind is Separation of Concerns (SoC). NestJS, with its modular architecture, makes applying SoC almost effortless — but understanding why it matters and how to use it properly will help you write cleaner, testable, and future-proof code.
What is Separation of Concerns and Why it Matters?
The basic idea is:
A program should be divided into distinct sections, where each section addresses a single responsibility.