DRY + KISS + YAGNI — how the three principles complement each other

DRY, KISS, and YAGNI work together to keep your code clean and maintainable. They each attack a different problem. DRY says don't repeat yourself, so if you have the same business logic in two places, extract it into a single method. KISS says keep it simple, so don't over-engineer with unnecessary design patterns or abstraction layers. YAGNI says you aren't gonna need it, so don't build features for hypothetical future requirements. Together, they guide you to write the minimum code necessary to solve today's problem in the clearest way possible. For example, imagine you're building a user registration feature. YAGNI says don't add password reset or social login yet if they're not in the current sprint. KISS says don't build an abstract factory for user validation if you only have one validation rule today. DRY says if you're checking email format in both the controller and the service, move that check into a single utility method. They reinforce each other. YAGNI prevents you from building five storage backends you don't need. KISS keeps the one you do need straightforward. DRY makes sure its logic lives in one place. There's some tension sometimes. For instance, eliminating duplication with DRY might require abstraction that hurts readability, violating KISS. In those cases, you need judgment. But overall, they're a unified mindset: write less code, make it simple, don't repeat yourself.