🚀 Low-Level Design (LLD) Mastery Repository

A curated collection of object-oriented design problems, SOLID principles, real-world LLD systems, and full implementations of Creational, Structural, and Behavioral design patterns.
This repository reflects senior-level engineering thinking, clean architecture, and interview-ready solutions.

The goal is simple: build real engineering muscle for scalable system design, exactly how top tech companies expect.

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📌 What This Repository Demonstrates

🔹 Object-Oriented Programming Mastery

• Encapsulation
• Abstraction
• Inheritance
• Polymorphism
• Interface-driven design
• Composition over inheritance
• Clean modular architecture

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🔹 SOLID Principles (With Real Implementations)

• Single Responsibility
• Open–Closed
• Liskov Substitution
• Interface Segregation
• Dependency Inversion

Every principle is demonstrated through code + reasoning, not theory.

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🎨 Design Pattern Coverage

🧱 Creational Patterns

• Factory
• Abstract Factory
• Builder
• Prototype
• Singleton

🏗 Structural Patterns

• Adapter
• Composite
• Decorator
• Proxy
• Facade

🎛 Behavioral Patterns

• Strategy
• Observer
• Template Method
• Iterator
• Command

Each pattern includes real-world problems and clean C++ implementations.

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📂 Repository Structure

LLD/
 ├── WEEK04  → Core OOP, inheritance, virtual functions, polymorphism  
 ├── WEEK05  → Strategy, Factory, interface-driven design  
 ├── WEEK06  → Behavioral patterns & architecture thinking  
 └── WEEK07  → Multi-module system-style LLD designs  

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🟦 WEEK 04 – OOP & Architecture

Focus:

• Inheritance models
• Dynamic dispatch
• VTables & runtime polymorphism
• Extensible class hierarchies

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🟩 WEEK 05 – Design Patterns (Part 1)

Includes:

• Strategy Pattern
• Factory Pattern
• Interface-driven programming
• Replace-if-else-with-polymorphism design

Mapped to real examples: payments, notifications, loggers.

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🟨 WEEK 06 – Behavioral Architecture

Includes:

• Observer-like updates
• Template method flows
• Multi-class orchestration
• Decoupling execution logic

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🟪 WEEK 07 – System-Level Design Thinking

Includes:

• Modular LLD structure
• Dependency flow
• Domain-driven class design

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🎯 Why This Repository Stands Out

This repo proves mastery in:
✔ Clean OOP architecture
✔ Applying correct design patterns
✔ Writing scalable, maintainable code
✔ Communicating design decisions like a senior engineer
✔ Solving LLD interview problems end-to-end

This is exactly what FAANG-style interviews expect.

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🚀 Upcoming Additions

• Parking Lot System
• Netflix LLD
• Elevator System
• Ride Sharing System
• Rate Limiter
• Pub/Sub System
• In-memory Database

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📞 Contact

Ahmar Faraz
Software Engineer
GitHub: https://github.com/iamahmarfaraz
LinkedIn: https://www.linkedin.com/in/iamahmarfaraz/