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Low-Level Design (LLD) — Complete Preparation Guide

Maps a 4-week study plan for low-level design interviews, covering OOP, design patterns, UML, and practice problems.

Tejoooo
May 2, 2026
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ai
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What this file does

Maps a 4-week study plan for low-level design interviews, covering OOP, design patterns, UML, and practice problems.

When to use it

  • Preparing for LLD rounds at companies like Microsoft or Amazon
  • Structuring self-study for object-oriented design interviews
  • Reviewing core design patterns and SOLID principles
  • Finding curated resources and practice platforms for LLD

Low-Level Design (LLD) — Complete Preparation Guide

📌 Table of Contents

🧩 What is Low-Level Design?

Low-Level Design (LLD) focuses on detailed class structures, interactions, and internal component architecture.

While HLD tells what the system contains,
LLD tells how each component works internally.

LLD includes:

  • Class diagrams
  • Sequence diagrams
  • Interfaces
  • Inheritance & composition
  • Object modeling
  • Applying design patterns

⭐ Why LLD Is Important

  • Shows your ability to convert requirements → code-ready structure
  • Ensures scalable and maintainable software
  • Highly tested in companies like Microsoft, Amazon, Uber, Swiggy, Atlassian

🏗 How to Prepare for LLD Interviews

  1. Master OOP fundamentals
  2. Understand SOLID & design principles
  3. Learn 8–12 core design patterns
  4. Practice real LLD problems
  5. Draw UML class diagrams
  6. Study GitHub repositories
  7. Watch LLD breakdowns on YouTube

📚 LLD Concepts You Must Know

1. Core OOP

  • Abstraction
  • Encapsulation
  • Inheritance
  • Polymorphism

2. Design Principles

  • SOLID
  • DRY
  • KISS
  • YAGNI
  • Composition > Inheritance

3. Design Patterns

Most commonly asked:

  • Singleton
  • Factory + Abstract Factory
  • Strategy
  • Observer
  • Decorator
  • Adapter
  • Proxy
  • Builder

4. UML

  • Class diagrams
  • Sequence diagrams
  • Activity diagrams

📝 Common LLD Interview Problems

  • Parking Lot System
  • Elevator System
  • Restaurant / Food Delivery App
  • Hotel Management System
  • Library Management
  • Splitwise
  • Uber / Ola Ride Booking
  • Snake and Ladder
  • Chess / Tic Tac Toe
  • Notification Service
  • Logging Framework
  • Rate Limiter (Token Bucket / Leaky Bucket)

🌐 Free Resources (Websites & Documentation)

Websites

🎥 Best YouTube Channels for LLD

💻 Practice Platforms

🗺 Preparation Roadmap

Week 1 — OOP + Design Principles

  • Master OOP
  • Learn SOLID
  • Draw UML diagrams

Week 2 — Design Patterns

  • Study & implement 8–12 patterns

Week 3 — Full LLD Case Studies

  • Parking Lot
  • Elevator
  • Library
  • Ride Booking

Week 4 — Mock Interviews

  • Solve 1 problem/day
  • Explain thought process
  • Focus on extensibility

🎁 Need this as a PDF, PPT, or Word?

Tell me the format, and I’ll generate it for you.

What's inside

9 sections: definition, importance, preparation steps, concepts, problems, resources, YouTube channels, platforms, roadmap

Change this for your project

  • Replace Tejoooo/Logic-Building-Series with your own repository name if forking
  • Replace YouTube channel links like https://www.youtube.com/@sudhanshuchannel with your preferred creators
  • Replace resource URLs like https://interviewready.io with your own curated list

Where it goes

Save in docs/ or the repository root. Gives agents and new contributors a map of the codebase.

Worth borrowing

  • Week-by-week roadmap with concrete deliverables per week
  • Categorized resource list separating websites, videos, and practice platforms

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