When should you apply a design pattern?

• A. Always apply for every problem.
• B. Apply when it clarifies structure or reduces complexity without overengineering.
• C. Never apply; design patterns are outdated.
• D. Only apply when the codebase is already over-engineered.

Answer: (B)

Design patterns are tools for organizing code when they genuinely make the design clearer and reduce complexity. They should be used when you can see that a pattern will improve structure, decoupling, or the ability to extend or modify behavior, without adding unnecessary layers or boilerplate. In other words, apply a pattern to achieve clarity and flexibility, not as a reflex.

If applying a pattern would merely add indirection or complexity without real benefits, it’s better to skip it. Patterns aren’t outdated or a cure-all; they’re helpful when they fit the problem and the team’s needs. And you don’t have to wait for a bloated codebase to justify them—patterns can prevent over-engineering by providing clean, deliberate ways to manage change.