In LLD interviews, knowing design patterns is less important than knowing when to use them and why. In most interviews, you are evaluated on your design judgement and not on how many patterns you know.

Most candidates either force patterns into simple problems or avoid them completely and end up with rigid code. The right approach is problem-first: spot the design pain point (messy object creation, changing behavior, tight coupling, hard-to-extend flow), then choose the pattern that directly solves it.

In this chapter, you’ll learn a practical way to recognize these signals, map them to the right patterns, and explain your choice clearly, so your design feels intentional, clean, and extensible.