Software Design
Software Design What are Design Principles?
Design principles are guidelines that help you make better decisions when writing and organizing code. They’re not strict rules to follow blindly, but rather a set of ideas that, when applied thoughtfully, lead to software that is easier to read, change, and extend.
Think of design principles as accumulated wisdom from decades of software development. They capture lessons learned from countless projects, distilled into memorable concepts that you can apply to your own work.
Why Design Principles Matter
Writing code that works is one thing. Writing code that remains easy to work with over time is another challenge entirely.
Without guiding principles, codebases tend to grow in unpredictable ways. Classes become bloated with unrelated responsibilities, changes in one place break things elsewhere, and you could spend more time deciphering existing code than writing new features.
Design principles help you avoid these pitfalls. They give you a framework for evaluating your decisions: Is this class doing too much? Am I repeating myself unnecessarily? Could this be simpler?
Common Design Principles
Several design principles have stood the test of time and are widely recognized across the industry.
SOLID is a collection of five principles for object-oriented design, covering topics like single responsibility, open/closed behavior, and dependency management. These principles help you create classes that are focused, flexible, and easy to test.
DRY (Don’t Repeat Yourself) encourages you to avoid duplicating knowledge in your system. When the same logic exists in multiple places, changes become error-prone and inconsistencies creep in.
KISS (Keep It Simple, Stupid) reminds you that simplicity should be a goal in itself. Complex solutions are harder to understand, debug, and maintain. If a simpler approach solves the problem, prefer it.
YAGNI (You Aren’t Gonna Need It) warns against building features before you actually need them. Code written for hypothetical scenarios often ends up unused or wrong when the real requirements emerge.
Separation of Concerns applies at the architectural level: different parts of your system should handle different responsibilities. For example, separating presentation, business logic, and data access (as in MVC), or keeping frontend and backend independent. When concerns are properly separated, you can change one aspect of your application without affecting others.
Applying Design Principles
Knowing design principles is the easy part. Applying them well takes practice and judgment.
The key is balance. Following DRY too strictly can lead to premature abstractions. Obsessing over SOLID can result in an explosion of tiny classes that are hard to navigate. Design principles sometimes conflict with each other, and part of becoming a better developer is learning when to prioritize one over another.
Start by recognizing code smells: signs that something might be wrong. A method that’s too long, a class that keeps changing for different reasons, or duplicated logic scattered across files. These are opportunities to apply design principles and improve your code incrementally.
Conclusion
Design principles are tools for thinking, not laws to enforce. They help you ask the right questions about your code and guide you toward solutions that will age well. Understand these principles and practice their application, to develop an intuition for writing software that is clean, maintainable, and ready for whatever changes come next.