Low-Level Design (LLD) Practices

This repository contains practical implementations of Low-Level System Designs. The primary objective is to translate high-level system requirements into robust, extensible, and scalable object-oriented code, adhering to SOLID principles and standard GoF design patterns.

Reference Material

The core concepts and problem statements implemented in this repository are heavily inspired by Soumyajit Bhattacharyay's LLD Playlist.

Core Design Principles Applied

Across all projects in this repository, the following architectural principles are strictly enforced:

• Single Responsibility Principle (SRP): Classes have one reason to change. Data access is decoupled from business logic.
• Open/Closed Principle (OCP): Systems are designed to be extensible (e.g., adding new payment methods or notification types) without modifying existing source code.
• Liskov Substitution Principle (LSP): Base classes and interfaces are strictly adhered to by derived entities to prevent runtime behavior mutations.
• Interface Segregation Principle (ISP): Fat interfaces are broken down into specific, client-focused contracts.
• Dependency Inversion Principle (DIP): High-level modules depend on abstractions (Interfaces/Abstract Classes), not concrete implementations, enabling seamless Dependency Injection.

Technology Stack

• Language: TypeScript
• Environment: Node.js
• Configuration: tsconfig.json configured for strict typing.

Projects Implemented

Currently, the following systems have been modeled:

• 📚 Library Management System: Manages book collections, member subscriptions, and lending processes. (See Library-Management-System/code.ts)
• 🎟️ BookMyShow: A movie ticket booking platform handling theaters, shows, and seat reservations. (See book-my-show/index.ts)
• 🏨 Hotel Management System: Systems for managing room bookings, housekeeping, and guest services. (See hotel-management-system/code.ts)

Getting Started

To run these projects locally:

1. Clone the repository:

   git clone https://github.com/hkumar3b/LLD.git
   cd low-level-design

2. Install dependencies:

   npm install

3. Run a specific project: Use the predefined npm scripts:

   npm run bms    # BookMyShow
   npm run lms    # Library Management System
   npm run hotel  # Hotel Management System

   Or use ts-node directly via npx:

   npx ts-node book-my-show/index.ts