⚙️ Low-Level Design (LLD)
Design classes, components, and interactions at the code level — SOLID principles, all 23 GoF design patterns, concurrency, and real interview case studies.
Track A — Module Map
SOLID + OOP + UML
5 SOLID principles, OOP pillars (Abstraction, Encapsulation, Inheritance, Polymorphism), UML class & sequence diagrams.
Creational Patterns
5 patterns: Singleton, Factory Method, Abstract Factory, Builder, Prototype — when to use each, pitfalls, real-world examples.
Structural Patterns
7 patterns: Adapter, Bridge, Composite, Decorator, Facade, Flyweight, Proxy — structural composition and interface shaping.
Behavioral Patterns
11 patterns: Chain of Responsibility, Command, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, Visitor, Interpreter.
Concurrency in LLD
Thread safety, synchronization primitives, Producer-Consumer, Reader-Writer, Thread Pool, deadlock detection and prevention.
LLD Case Studies
6 full systems: Chess Game, Elevator, Library Management, Food Ordering, Parking Lot, Hotel Booking — applying all patterns end-to-end.
Pattern Coverage Summary
| Category | Patterns | Module | Status |
|---|---|---|---|
| Creational (5) | Singleton, Factory Method, Abstract Factory, Builder, Prototype | A2 | ✅ Complete |
| Structural (7) | Adapter, Bridge, Composite, Decorator, Facade, Flyweight, Proxy | A3 | ✅ Complete |
| Behavioral (11) | CoR, Command, Iterator, Mediator, Memento, Observer, State, Strategy, Template, Visitor, Interpreter | A4 | ✅ Complete |
| SOLID + OOP | SRP, OCP, LSP, ISP, DIP + 4 OOP pillars + UML | A1 | ✅ Complete |
| Concurrency | Thread safety, locks, semaphores, concurrent patterns | A5 | ✅ Complete |
| LLD Systems | Chess, Elevator, Library, Food Ordering, Parking Lot, Hotel | A6 | ✅ Complete |