LLD · CS Fundamentals
LLD (Low-Level Design) Interview Guide
LLD interviews ask you to design the class structure for a real system — a parking lot, a chess engine, a booking flow — applying SOLID principles and picking the right design patterns, usually with a follow-up on making it thread-safe. The evaluation is on your class boundaries and extensibility, not on producing UML from memory.
What to actually study
- SOLID principles — applied to a real class hierarchy, not recited
- Design patterns — Strategy, Singleton, and when each earns its complexity
- Concurrency-safe object design — thread safety, race conditions, optimistic vs. pessimistic locking at the class level
- End-to-end class design for a stateful system (parking lot, chess engine, booking flow)
Real questions from Ediky's bank
From the shared System Design topic, these lean LLD (class-level design, not distributed systems):
- "Design the Class Architecture for a Two-Player Chess Engine"
- "Schema Design for a Multiplex Seat-Hold and Booking Flow"
How to study on Ediky
Start with Ediky's 28-lecture LLD video course for structured coverage, then use the design-style questions in CS Fundamentals for applied practice — filter by "System Design" and focus on the class-design questions over the distributed-systems ones (see the HLD guide for that half).
Start the LLD video course
28 lectures covering class design, SOLID, and design patterns for interviews.
Open Learning Resources