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Learn Low Level Design (LLD) and prepare for interviews using free resources.

Fundamental Concepts

• Basics OOP Concepts
• SOLID Principles with Pictures
• SOLID Principles with Code
• DRY Principle
• YAGNI Principle
• KISS Principle
• Coursera - Object-Oriented Design

Design Patterns

Creational Patterns

• Singleton
• Factory Method
• Abstract Factory
• Builder

Structural Patterns

• Adapter
• Facade
• Decorator
• Composite

Behavioral Patterns

• Strategy
• Iterator
• Observer
• Template Method
• Command
• State

UML

• Class Diagram
• Use Case Diagram
• Sequence Diagram
• Activity Diagram
• State Machine Diagram

Low Level Design Interview Problems

Easy

• Design Parking Lot
• Design a Vending Machine
• Design Stack Overflow
• Design Logging Framework
• Design Coffee Vending Machine
• Design Traffic Signal Control System
• Design a Task Management System

Medium

• Design Pub Sub System
• Design Tic Tac Toe Game
• Design Car Rental System
• Design an ATM
• Design Hotel Management System
• Design LinkedIn
• Design a Social Network like Facebook
• Design an Elevator System
• Design a Library Management System
• Design Restaurant Management System
• Design Airline Management System
• Design a Digital Wallet System
• Design an Online Auction System
• Design a Concert Ticket Booking System
• Design a Cache using LRU Eviction Policy

Hard

• Design Movie Ticket Booking System
• Design Splitwise
• Design a Snake and Ladder game
• Design Online Shopping System like Amazon
• Design Online Stock Brokerage System
• Design CricInfo
• Design Chess Game
• Design Ride-Sharing Service (like Uber)
• Design Online Food Delivery Service (like Swiggy)
• Design Music Streaming Service (like Spotify)
• Design University Course Registration System

Books

• Head First Design Patterns
• Clean Code
• Refactoring: Improving the Design of Existing Code

Additional resources

• Coursera - Design Patterns
• Github - Awesome Design Patterns