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19,057 edges
1,821 files
⚖ GPL-3.0
391 documented · 5%
1 cross-repo links
● updated 5mo ago★ 26,20243 open issues
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README
This repository contains resources to learn Low Level Design (LLD) / Object Oriented Design (OOD) and prepare for interviews. It covers OOP fundamentals, design patterns, UML, concurrency and commonly asked interview questions.
👉 For a better and more comprehensive experience, checkout the LLD page at AlgoMaster.io
🧱 OOP Fundamentals
🔗 Class Relationships
🧭 Design Principles
- DRY Principle
- YAGNI Principle
- KISS Principle
- SOLID Principles with Pictures
- SOLID Principles with Code
🧩 Design Patterns
| Creational Patterns | Structural Patterns | Behavioral Patterns |
|---|---|---|
| Singleton | Adapter | Iterator |
| Factory Method | Bridge | Observer |
| Abstract Factory | Composite | Strategy |
| Builder | Decorator | Command |
| Prototype | Facade | State |
| Flyweight | Template Method | |
| Proxy | Visitor | |
| Mediator | ||
| Memento | ||
| Chain of Responsibility |
🗂️ UML
⏱️ Concurrency and Multi-threading Concepts
Concurrency 101
- Introduction to Concurrency
- Concurrency vs Parallelism
- Processes vs Threads
- Thread Lifecycle and States
- Race Conditions and Critical Sections
Synchronization Primitives
- Mutex (Mutual Exclusion)
- Semaphores
- Condition Variables
- Coarse-grained vs Fine-grained Locking
- Reentrant Locks
- Try-Lock and Timed Locking
- Compare-and-Swap (CAS)
Concurrency Challenges
Concurrency Patterns
✅ How to Answer a LLD Interview Problem
💻 Low Level Design Interview Problems
Easy Problems
- Design Parking Lot
- Design Stack Overflow
- Design a Vending Machine
- Design Logging Framework
- Design Traffic Signal Control System
- Design Coffee Vending Machine
- Design a Task Management System
Medium Problems
- Design ATM
- Design LinkedIn
- Design LRU Cache
- Design Tic Tac Toe Game
- Design Pub Sub System
- Design an Elevator System
- Design Car Rental System
- Design an Online Auction System
- Design Hotel Management System
- Design a Digital Wallet Service
- Design Airline Management System
- Design a Library Management System
- Design a Social Network like Facebook
- Design Restaurant Management System
- Design a Concert Ticket Booking System
Hard Problems
- Design CricInfo
- Design Splitwise
- Design Chess Game
- Design a Snake and Ladder game
- Design Ride-Sharing Service like Uber
- Design Course Registration System
- Design Movie Ticket Booking System
- Design Online Shopping System like Amazon
- Design Online Stock Brokerage System
- Design Music Streaming Service like Spotify
- Design Online Food Delivery Service like Swiggy
⏱️ Concurrency and Multi-threading Problems
- Print FooBar Alternately
- Print Zero Even Odd
- Fizz Buzz Multithreaded
- Building H2O Molecule
- Design Thread-Safe Cache with TTL
- Design Concurrent HashMap
- Design Thread-Safe Blocking Queue
- Design Concurrent Bloom Filter
- Multi-threaded Merge Sort
📇 Courses
📚 Books
📩 Newsletter
Additional resources
🤝 Contributing
Contributions are welcome! If you'd like to add a new problem, improve existing content, or fix errors:
1. Fork the repository
2. Create a feature branch: git checkout -b feature/your-feature-name
3. Commit your changes: git commit -m 'Add some feature'
4. Push to the branch: git push origin feature/your-feature-name
5. Submit a pull request
Please make sure to update Readme files and documentation as appropriate.
If you find this resource helpful, please give it a star and share it with others!
Extension points exported contracts — how you extend this code
TaskSortingStrategy (Interface)
(no doc) [12 implementers]
solutions/typescript/src/TaskManagement/SortingStrategy/TaskSortingStrategy.ts
BillComponent (Interface)
(no doc) [6 implementers]
solutions/java/src/restaurantmanagementsystem/decorator/BillComponent.java
Subscription (Interface)
(no doc) [8 implementers]
design-patterns/java/factory/subscription/Subscription.java
Beverage (Interface)
Beverage defines the interface for all beverages [3 implementers]
design-patterns/golang/decorator/beverage.go
Transaction (Interface)
(no doc) [4 implementers]
solutions/golang/atm/transaction.go
SignalState (Interface)
(no doc) [6 implementers]
solutions/typescript/src/TrafficSignalSystem/SignalState/SignalState.ts
browse all types & interfaces →
Core symbols most depended-on inside this repo
↓ 81 filesFolder
design-patterns/Javascript/Structural Pattern/Composite Design Pattern/folder.js
↓ 72 filesSignalStatesolutions/typescript/src/TrafficSignalSystem/SignalState/SignalState.ts
↓ 65 filesLogAppendersolutions/java/src/loggingframework/strategies/appender/LogAppender.java
↓ 62 filesSubscribersolutions/java/src/pubsubsystem/subscriber/Subscriber.java
↓ 53 filesGameObserversolutions/java/src/tictactoe/observer/GameObserver.java
↓ 45 filesNotificationObserversolutions/java/src/linkedin/observer/NotificationObserver.java
Shape
Languages
Java40%
Python35%
Go16%
TypeScript9%
Modules by API surface
solutions/python/taskmanagementsystem/task.py34 symbols
solutions/java/src/taskmanagementsystem/models/Task.java34 symbols
solutions/golang/vendingmachine/state.go31 symbols
design-patterns/Javascript/Creational Pattern/AbstractFactory Design Pattern/abstract.js30 symbols
solutions/golang/stackOverFlow/types.go29 symbols
solutions/python/stackoverflow/content.py27 symbols
solutions/python/vendingmachine/states.py26 symbols
solutions/python/ridesharingservice/trip_states.py25 symbols
solutions/python/ridesharingservice/trip.py25 symbols
solutions/python/coffeevendingmachine/states.py25 symbols
solutions/python/coffeevendingmachine/coffee.py25 symbols
solutions/java/src/ridesharingservice/entities/Trip.java25 symbols
Dependencies from manifests, versioned
org.junit.jupiter:junit-jupiter1×
@types/node20.10.0 · 1×
node-fetch3.3.1 · 1×
tsx4.7.1 · 1×
uuid11.1.0 · 1×
For agents
$ claude mcp add awesome-low-level-design \
-- python -m otcore.mcp_server <graph>