Are these real interview questions?

Yes - every problem in the list has been reported by engineers who interviewed at the companies tagged on each problem. They reflect the actual vocabulary, scope, and constraints that interviewers use when asking LLD questions.

What is the difference between Easy, Medium, and Hard?

Easy problems involve a single well-defined system (Parking Lot, Vending Machine) where the class structure is mostly obvious. Medium problems involve multiple interacting subsystems or a non-trivial design decision. Hard problems require distributed thinking, concurrency handling, or a deep understanding of multiple design patterns working together.

Can I solve these problems in the LLDCanvas editor?

Yes - each problem page links directly to the editor so you can start drawing your UML class diagram immediately. Your diagram autosaves and you can share it with collaborators for a mock interview session.

Do I need an account to view the problems?

No - all problems are publicly visible. An account is needed to save your diagram solutions, access hints, join community discussions, and run code.

How are community discussions different from community solutions?

Discussions are freeform - you can ask questions, share partial ideas, paste code, or critique an approach. They are not scored or ranked. The goal is learning through dialogue, not upvotes.

LLD Interview Questions - 110+ Low-Level Design Practice Problems

¶04 - Practice Problems

curated LLD
interview problems

Every question that comes up in real Low-Level Design interviews - Parking Lot to Uber, ATM to distributed rate limiters - with difficulty, real-world context, and the companies known to ask it.

Problem index

Parking Lot System

Library Management System

ATM Machine

Elevator System

Vending Machine

Snake and Ladder Game

Tic-Tac-Toe

Chess Game

Deck of Cards / Blackjack

Traffic Light System

Logging Framework

Rate Limiter

Pub-Sub Messaging System

Restaurant Table Reservation System

Parking Lot System ·Library Management System ·ATM Machine ·Elevator System ·Vending Machine ·Snake and Ladder Game ·Tic-Tac-Toe ·Chess Game ·Deck of Cards / Blackjack ·Traffic Light System ·Logging Framework ·Rate Limiter ·Pub-Sub Messaging System ·Restaurant Table Reservation System ·Basic Calculator with Undo/Redo ·In-Memory File System ·Job Scheduler (Cron-like Task Runner) ·Quiz / Trivia Game Engine ·Digital Wallet (Single Currency) ·Meeting Room Booking System ·Contact Management System (Address Book) ·Ludo Board Game ·Memory Matching Card Game ·Cafeteria Self-Checkout Billing System ·Stopwatch & Lap Timer ·Simple LRU Cache ·Weather Station Monitoring System ·Text Editor with Undo/Redo ·Battleship Game ·Coffee Vending Machine ·Task Management System ·Twitter / X ·WhatsApp Messenger ·Netflix Streaming Service ·Google Drive ·Instagram ·Uber (Full Design) ·YouTube ·URL Shortener (bit.ly) ·Distributed Cache (Redis-like) ·Payment Gateway (Stripe-like) ·Search Autocomplete System ·Real-Time Gaming Leaderboard ·Distributed Message Queue (Kafka-like) ·API Gateway ·Ride Sharing — Backend Deep Dive ·Web Crawler ·Typeahead / Instant Search ·Facebook / Social Graph ·Yelp / Local Business Search ·Google Docs — Collaborative Real-Time Text Editor ·Distributed Rate Limiter (Multi-Node) ·News Feed Ranking System ·Distributed Job Scheduler (Airflow-like) ·Distributed Notification Fanout System ·Content Delivery Network (CDN) ·Distributed Lock Manager (Zookeeper-like) ·Live Video Streaming Platform (Twitch-like) ·Ad Click Tracking & Billing System ·Distributed Task Queue (Celery/Sidekiq-like) ·Distributed Unique ID Generator (Snowflake-like) ·Fraud Detection System ·Search Engine Indexing System ·Distributed Metrics & Monitoring System ·Distributed Session Store ·Multiplayer Game Matchmaking System ·Real-Time Collaborative Code Editor ·Course Registration System ·Hotel Booking System ·Movie Ticket Booking ·Food Delivery App ·Amazon Locker System ·Splitwise / Expense Splitter ·Cab Booking System ·Online Shopping Cart ·Online Stock Brokerage ·Car Rental System ·Flight Reservation System ·Stack Overflow / Q&A Platform ·LinkedIn / Professional Network ·Music Streaming (Spotify) ·Online Code Judge (LeetCode) ·Notification Service ·Coupon & Discount System ·Inventory Management System ·Video Conferencing (Zoom) ·Pastebin / Code Snippet Sharing ·Cricket Scoreboard / Live Scoring ·Airline Boarding & Seat Assignment System ·Peer-to-Peer Digital Wallet System ·Restaurant POS & Kitchen Display System ·E-Book Lending Platform ·Online Auction System ·Hospital Appointment Scheduling System ·Gym Membership & Class Booking System ·Online Survey / Form Builder ·Event Ticketing Platform ·Podcast Platform ·Cloud File Sync Client (Dropbox-like) ·Recipe & Meal Planning App ·Fitness Tracker App ·Multiplayer Tic-Tac-Toe with Matchmaking ·Elevator Group Control System (Multiple Elevators) ·Online Polling / Voting Platform ·Warehouse Order Fulfillment System ·Customer Support Ticketing System ·Loyalty Points & Rewards Program ·Social Event Planning App (Meetup-like) ·Airline Management System ·Restaurant Management System ·Parking Lot System ·Library Management System ·ATM Machine ·Elevator System ·Vending Machine ·Snake and Ladder Game ·Tic-Tac-Toe ·Chess Game ·Deck of Cards / Blackjack ·Traffic Light System ·Logging Framework ·Rate Limiter ·Pub-Sub Messaging System ·Restaurant Table Reservation System ·Basic Calculator with Undo/Redo ·In-Memory File System ·Job Scheduler (Cron-like Task Runner) ·Quiz / Trivia Game Engine ·Digital Wallet (Single Currency) ·Meeting Room Booking System ·Contact Management System (Address Book) ·Ludo Board Game ·Memory Matching Card Game ·Cafeteria Self-Checkout Billing System ·Stopwatch & Lap Timer ·Simple LRU Cache ·Weather Station Monitoring System ·Text Editor with Undo/Redo ·Battleship Game ·Coffee Vending Machine ·Task Management System ·Twitter / X ·WhatsApp Messenger ·Netflix Streaming Service ·Google Drive ·Instagram ·Uber (Full Design) ·YouTube ·URL Shortener (bit.ly) ·Distributed Cache (Redis-like) ·Payment Gateway (Stripe-like) ·Search Autocomplete System ·Real-Time Gaming Leaderboard ·Distributed Message Queue (Kafka-like) ·API Gateway ·Ride Sharing — Backend Deep Dive ·Web Crawler ·Typeahead / Instant Search ·Facebook / Social Graph ·Yelp / Local Business Search ·Google Docs — Collaborative Real-Time Text Editor ·Distributed Rate Limiter (Multi-Node) ·News Feed Ranking System ·Distributed Job Scheduler (Airflow-like) ·Distributed Notification Fanout System ·Content Delivery Network (CDN) ·Distributed Lock Manager (Zookeeper-like) ·Live Video Streaming Platform (Twitch-like) ·Ad Click Tracking & Billing System ·Distributed Task Queue (Celery/Sidekiq-like) ·Distributed Unique ID Generator (Snowflake-like) ·Fraud Detection System ·Search Engine Indexing System ·Distributed Metrics & Monitoring System ·Distributed Session Store ·Multiplayer Game Matchmaking System ·Real-Time Collaborative Code Editor ·Course Registration System ·Hotel Booking System ·Movie Ticket Booking ·Food Delivery App ·Amazon Locker System ·Splitwise / Expense Splitter ·Cab Booking System ·Online Shopping Cart ·Online Stock Brokerage ·Car Rental System ·Flight Reservation System ·Stack Overflow / Q&A Platform ·LinkedIn / Professional Network ·Music Streaming (Spotify) ·Online Code Judge (LeetCode) ·Notification Service ·Coupon & Discount System ·Inventory Management System ·Video Conferencing (Zoom) ·Pastebin / Code Snippet Sharing ·Cricket Scoreboard / Live Scoring ·Airline Boarding & Seat Assignment System ·Peer-to-Peer Digital Wallet System ·Restaurant POS & Kitchen Display System ·E-Book Lending Platform ·Online Auction System ·Hospital Appointment Scheduling System ·Gym Membership & Class Booking System ·Online Survey / Form Builder ·Event Ticketing Platform ·Podcast Platform ·Cloud File Sync Client (Dropbox-like) ·Recipe & Meal Planning App ·Fitness Tracker App ·Multiplayer Tic-Tac-Toe with Matchmaking ·Elevator Group Control System (Multiple Elevators) ·Online Polling / Voting Platform ·Warehouse Order Fulfillment System ·Customer Support Ticketing System ·Loyalty Points & Rewards Program ·Social Event Planning App (Meetup-like) ·Airline Management System ·Restaurant Management System ·

#Problem

Questions people ask