Low-Level Design Guide: Learning Roadmap

You're staring at an LLD interview question: "Design a parking lot system." You know OOP theory, but translating real-world problems into clean class hierarchies feels like a different skill entirely. The interviewer wants SOLID principles, design patterns, and interface contracts — but where do you even start?

The gap between knowing OOP concepts and applying them in interview scenarios is where most engineers stumble. This roadmap bridges that gap through a decision-tree approach: eight carefully sequenced problems that build OOP design fluency from state machines to production-grade implementations in Java Spring Boot.

TLDR: Follow the decision tree to find your learning path through 8 LLD problems, from OOP foundations to production systems, based on your timeline and interview focus.