PrepKitBeta
DSALLDSystem DesignLanguages
PrepKit

© 2026 PrepKit. All rights reserved.

Made with ❤︎ by Jasir

Low-Level Design

A comprehensive guide to the Object-Oriented Design interview, covering the principles, patterns, and case studies you need to succeed.

Object-Oriented Programming (OOP)

Fundamental concepts of OOP that form the backbone of LLD.

  • Encapsulation
  • Abstraction
  • Inheritance
  • Polymorphism

SOLID Principles

Five design principles to make software designs more understandable, flexible, and maintainable.

  • Single Responsibility Principle (SRP)
  • Open/Closed Principle (OCP)
  • Liskov Substitution Principle (LSP)
  • Interface Segregation Principle (ISP)
  • Dependency Inversion Principle (DIP)

Creational Design Patterns

Patterns that deal with object creation mechanisms.

  • Singleton
  • Factory Method
  • Abstract Factory
  • Builder
  • Prototype

Structural Design Patterns

Patterns that ease the design by identifying a simple way to realize relationships between entities.

  • Adapter
  • Decorator
  • Facade
  • Proxy
  • Composite
  • Bridge
  • Flyweight

Behavioral Design Patterns

Patterns that are concerned with algorithms and the assignment of responsibilities between objects.

  • Chain of Responsibility
  • Command
  • Iterator
  • Observer
  • Strategy
  • State
  • Template Method
  • Visitor
  • Mediator

UML & System Modelling

Learn to visualize, specify, construct, and document the artifacts of a software-intensive system.

  • Class Diagram
  • Sequence Diagram
  • Use Case Diagram
  • Activity Diagram

LLD Case Studies

Apply your knowledge to real-world problems.

  • Design a Vending Machine
  • Design a Parking Lot
  • Design a Library Management System
  • Design a Chess Game
  • Design a Ride-Sharing App