Design patterns are well-proven, reusable solutions to commonly occurring problems within a given context.

Knowing the catalogue of patterns (Singleton, Factory, Strategy, Observer) is like knowing the names of the tools. It's a start. But the mark of a master craftsman is not the ability to name the tools, but the wisdom to know precisely which one to choose for the job at hand, and, just as importantly, when to use no tool at all.

This chapter is about developing that wisdom. We will move beyond the "what" of design patterns and focus on the "why" and "when."

You will learn a practical framework for diagnosing design problems in your code and confidently selecting the pattern that provides the most elegant and maintainable solution.

We will also explore the Top 10 most commonly asked design patterns in LLD interviews.

1. Let the Problem Guide You