Low Level Design

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How to Pass Low Level Design Interviews in 2026

  • LRU Cache

    Problem Statement · Editorial Solution

  • Parking Lot System

    Problem Statement · Editorial Solution

  • Design HashMap

    Problem Statement · Editorial Solution

  • 2048 Game Implementation

    Problem Statement · Editorial Solution

  • 2D Vector Class

    Problem Statement · Editorial Solution

  • Access Control Tree

    Problem Statement · Editorial Solution

  • Access Management System

    Problem Statement · Editorial Solution

  • Account Balance Tracker

    Problem Statement · Editorial Solution

  • Account Management Service

    Problem Statement · Editorial Solution

  • Active Users in N Minutes

    Problem Statement · Editorial Solution

  • Actor Component Model

    Problem Statement · Editorial Solution

  • Alerting Engine Rules

    Problem Statement · Editorial Solution

  • All O`one Data Structure

    Problem Statement · Editorial Solution

  • API Billing & Usage System

    Problem Statement · Editorial Solution

  • API Rate Limiter

    Problem Statement · Editorial Solution

  • ASCII Canvas - Draw Rectangle

    Problem Statement · Editorial Solution

  • Async: Limit (Concurrency Control)

    Problem Statement · Editorial Solution

  • AsyncTaskQueue (Concurrency Control)

    Problem Statement · Editorial Solution

  • Autocomplete Utility

    Problem Statement · Editorial Solution

  • Avatar Component Loading Order

    Problem Statement · Editorial Solution

  • Background Job Processor with Retries

    Problem Statement · Editorial Solution

  • Banking Application

    Problem Statement · Editorial Solution

  • Banking Operations Debugging

    Problem Statement · Editorial Solution

  • Banking System (Progressive)

    Problem Statement · Editorial Solution

  • Banking System API

    Problem Statement · Editorial Solution

  • Basic Blockchain

    Problem Statement · Editorial Solution

  • Batching Utility with Timeout

    Problem Statement · Editorial Solution

  • Battleship Game Simulation

    Problem Statement · Editorial Solution

  • Bookstore Word Counter

    Problem Statement · Editorial Solution

  • Browser History Data Structure

    Problem Statement · Editorial Solution

  • Buffered File System

    Problem Statement · Editorial Solution

  • Buffered File Writer

    Problem Statement · Editorial Solution

  • Building Interface: Hospital and School

    Problem Statement · Editorial Solution

  • Burger Shop (Builder Pattern)

    Problem Statement · Editorial Solution

  • Caching Library with Pluggable Eviction Policies

    Problem Statement · Editorial Solution

  • Candidate Recruiter Management System

    Problem Statement · Editorial Solution

  • Card Transaction Authorization System

    Problem Statement · Editorial Solution

  • Cargo Shipping Calculator

    Problem Statement · Editorial Solution

  • CD With Symbolic Links

    Problem Statement · Editorial Solution

  • Central Banking Ledger

    Problem Statement · Editorial Solution

  • Chat Profanity Filter

    Problem Statement · Editorial Solution

  • Circuit Breaker

    Problem Statement · Editorial Solution

  • Circular Buffer

    Problem Statement · Editorial Solution

  • Cloud Billing System

    Problem Statement · Editorial Solution

  • Cloud Storage

    Problem Statement · Editorial Solution

  • Coffee Shop Decorator

    Problem Statement · Editorial Solution

  • Column Index

    Problem Statement · Editorial Solution

  • Comment Threading Model

    Problem Statement · Editorial Solution

  • Component Design: Virtualized List

    Problem Statement · Editorial Solution

  • Concurrent Money Transfer

    Problem Statement · Editorial Solution

  • Connect 4 Backend

    Problem Statement · Editorial Solution

  • Connect Four

    Problem Statement · Editorial Solution

  • Container Orchestrator

    Problem Statement · Editorial Solution

  • Cookie Manager

    Problem Statement · Editorial Solution

  • Coupon Redemption System

    Problem Statement · Editorial Solution

  • Credit Tracker with Expirations

    Problem Statement · Editorial Solution

  • Credit-Based Purchase Model

    Problem Statement · Editorial Solution

  • Critical Memory Alert Analysis

    Problem Statement · Editorial Solution

  • Custom Dynamic Array

    Problem Statement · Editorial Solution

  • Custom HashMap with Bulk Operations

    Problem Statement · Editorial Solution

  • Custom Playlist Picture System

    Problem Statement · Editorial Solution

  • Customer Support Leaderboard

    Problem Statement · Editorial Solution

  • DAG Task Graph

    Problem Statement · Editorial Solution

  • Data Source Difference Tracker

    Problem Statement · Editorial Solution

  • Data Stream as Disjoint Intervals

    Problem Statement · Editorial Solution

  • DataStream Guessing Game

    Problem Statement · Editorial Solution

  • Debounced Search Bar

    Problem Statement · Editorial Solution

  • Decorator Pattern Tax/Discount Calculator

    Problem Statement · Editorial Solution

  • Deep Copy Manager

    Problem Statement · Editorial Solution

  • Delayed Payment System

    Problem Statement · Editorial Solution

  • Design 3 Stacks in 1 Array

    Problem Statement · Editorial Solution

  • Design a 3D Binary Matrix with Efficient Layer Tracking

    Problem Statement · Editorial Solution

  • Design a Bank Account Class

    Problem Statement · Editorial Solution

  • Design a Credit Card Limit Manager

    Problem Statement · Editorial Solution

  • Design a Credit Tracker

    Problem Statement · Editorial Solution

  • Design A Leaderboard

    Problem Statement · Editorial Solution

  • Design a Logging Library

    Problem Statement · Editorial Solution

  • Design a Rate Limiter for an AI Hub

    Problem Statement · Editorial Solution

  • Design a Specialized Cache

    Problem Statement · Editorial Solution

  • Design a Stack with Increment Operation

    Problem Statement · Editorial Solution

  • Design a Tetris Game

    Problem Statement · Editorial Solution

  • Design a Text Editor

    Problem Statement · Editorial Solution

  • Design a Todo List

    Problem Statement · Editorial Solution

  • Design an Anagram Store

    Problem Statement · Editorial Solution

  • Design an ATM System

    Problem Statement · Editorial Solution

  • Design an Elevator Dispatcher

    Problem Statement · Editorial Solution

  • Design an Expression Tree With Evaluate Function

    Problem Statement · Editorial Solution

  • Design an ID Allocator

    Problem Statement · Editorial Solution

  • Design BigInteger

    Problem Statement · Editorial Solution

  • Design Browser History

    Problem Statement · Editorial Solution

  • Design Circular Deque

    Problem Statement · Editorial Solution

  • Design Circular Queue

    Problem Statement · Editorial Solution

  • Design File System

    Problem Statement · Editorial Solution

  • Design File System Find API

    Problem Statement · Editorial Solution

  • Design GPU Credits

    Problem Statement · Editorial Solution

  • Design Hit Counter

    Problem Statement · Editorial Solution

  • Design In-Memory Database

    Problem Statement · Editorial Solution

  • Design In-Memory File System

    Problem Statement · Editorial Solution

  • Design Linked List

    Problem Statement · Editorial Solution

  • Design Log Parser

    Problem Statement · Editorial Solution

  • Design Log Storage System

    Problem Statement · Editorial Solution

  • Design Playlist Data Structure

    Problem Statement · Editorial Solution

  • Design Retriable Function

    Problem Statement · Editorial Solution

  • Design Search Autocomplete System

    Problem Statement · Editorial Solution

  • Design Skip List

    Problem Statement · Editorial Solution

  • Design Spreadsheet With Undo Redo

    Problem Statement · Editorial Solution

  • Design Tic-Tac-Toe

    Problem Statement · Editorial Solution

  • Design Underground System

    Problem Statement · Editorial Solution

  • Detect Squares

    Problem Statement · Editorial Solution

  • Dinner Plate Stacks

    Problem Statement · Editorial Solution

  • Disk Space Manager

    Problem Statement · Editorial Solution

  • Distributed Lock Manager

    Problem Statement · Editorial Solution

  • Document Version Control System

    Problem Statement · Editorial Solution

  • Driver-Order Matching System

    Problem Statement · Editorial Solution

  • Elevator System

    Problem Statement · Editorial Solution

  • Encode and Decode TinyURL

    Problem Statement · Editorial Solution

  • Event Emitter

    Problem Statement · Editorial Solution

  • Expandable Array Implementation

    Problem Statement · Editorial Solution

  • Fault-Tolerant Redis Wrapper

    Problem Statement · Editorial Solution

  • File Collections Tracker

    Problem Statement · Editorial Solution

  • File Storage Query System

    Problem Statement · Editorial Solution

  • File Tree Management

    Problem Statement · Editorial Solution

  • Financial Ledger (Double-Entry Accounting)

    Problem Statement · Editorial Solution

  • Financial Stream Processing

    Problem Statement · Editorial Solution

  • Find Consecutive Integers from a Data Stream

    Problem Statement · Editorial Solution

  • First Unique Number

    Problem Statement · Editorial Solution

  • Flatten Nested List Iterator

    Problem Statement · Editorial Solution

  • Flight Booking System

    Problem Statement · Editorial Solution

  • Food Delivery Matching Engine

    Problem Statement · Editorial Solution

  • Fractional Share Inventory

    Problem Statement · Editorial Solution

  • Fraud Detection: Rolling Window Thresholds

    Problem Statement · Editorial Solution

  • Frequency and Distance Top-K Query System

    Problem Statement · Editorial Solution

  • Frequency Tracker

    Problem Statement · Editorial Solution

  • Game Lobby State Machine

    Problem Statement · Editorial Solution

  • Gameplay Ability System

    Problem Statement · Editorial Solution

  • Go Fish (Card Game)

    Problem Statement · Editorial Solution

  • Graph Implementation

    Problem Statement · Editorial Solution

  • Growing List (Dynamic Array)

    Problem Statement · Editorial Solution

  • Handling Concurrent Credit Deductions

    Problem Statement · Editorial Solution

  • Hash Table Implementation

    Problem Statement · Editorial Solution

  • Hierarchical Menu Price

    Problem Statement · Editorial Solution

  • High Frequency Sensor Data Aggregator

    Problem Statement · Editorial Solution

  • Hotel CRUD & Proximity Search

    Problem Statement · Editorial Solution

  • iCloud Photo Sync with Conflict Resolution

    Problem Statement · Editorial Solution

  • Idempotent Payment Processor

    Problem Statement · Editorial Solution

  • Idempotent Transaction Ledger

    Problem Statement · Editorial Solution

  • Immutable Class Implementation

    Problem Statement · Editorial Solution

  • Implement Queue using Array

    Problem Statement · Editorial Solution

  • Implement Queue using Stacks

    Problem Statement · Editorial Solution

  • Implement Stack Using Arrays

    Problem Statement · Editorial Solution

  • Implement Stack using Queues

    Problem Statement · Editorial Solution

  • Implementing Core Linux Commands

    Problem Statement · Editorial Solution

  • In-Memory Banking System

    Problem Statement · Editorial Solution

  • In-Memory Cloud Storage with Quotas

    Problem Statement · Editorial Solution

  • In-Memory Database

    Problem Statement · Editorial Solution

  • In-Memory Key-Value CRUD Store

    Problem Statement · Editorial Solution

  • In-Memory Ledger

    Problem Statement · Editorial Solution

  • In-Memory Load Balancer

    Problem Statement · Editorial Solution

  • In-Memory Message Broker

    Problem Statement · Editorial Solution

  • Input Remapping System

    Problem Statement · Editorial Solution

  • Insert Delete GetRandom O(1) - Duplicates allowed

    Problem Statement · Editorial Solution

  • Insurance Policy Logic Engine

    Problem Statement · Editorial Solution

  • Inventory and Item System

    Problem Statement · Editorial Solution

  • Inventory Management System

    Problem Statement · Editorial Solution

  • Inventory Manager

    Problem Statement · Editorial Solution

  • Jigsaw Puzzle Solver

    Problem Statement · Editorial Solution

  • K-Way Merge Iterator

    Problem Statement · Editorial Solution

  • Key Generation Service

    Problem Statement · Editorial Solution

  • Key-Value Store with TTL and Transactions

    Problem Statement · Editorial Solution

  • KV Store with Sliding Window QPS

    Problem Statement · Editorial Solution

  • Lazy Update Priority Queue

    Problem Statement · Editorial Solution

  • Library Management System

    Problem Statement · Editorial Solution

  • Lightweight Load Balancer

    Problem Statement · Editorial Solution

  • Loan State Machine

    Problem Statement · Editorial Solution

  • Locker Allocation System

    Problem Statement · Editorial Solution

  • Log Collection and Aggregation System

    Problem Statement · Editorial Solution

  • Log Monitoring and Alerting System

    Problem Statement · Editorial Solution

  • Log Parser Rolling Average Storage

    Problem Statement · Editorial Solution

  • Log-Query Stream Processor

    Problem Statement · Editorial Solution

  • Logger Rate Limiter

    Problem Statement · Editorial Solution

  • LRU Cache with Serialization

    Problem Statement · Editorial Solution

  • Mars Rover

    Problem Statement · Editorial Solution

  • Max Stack

    Problem Statement · Editorial Solution

  • Maximum Frequency Stack

    Problem Statement · Editorial Solution

  • Meeting Room Reservation System

    Problem Statement · Editorial Solution

  • Meeting Scheduler

    Problem Statement · Editorial Solution

  • Memory Allocator

    Problem Statement · Editorial Solution

  • Memory Efficient Circular Frame Buffer

    Problem Statement · Editorial Solution

  • Message Buffer with Flush Policy

    Problem Statement · Editorial Solution

  • Message Processing System

    Problem Statement · Editorial Solution

  • Micro-Deposit Verification

    Problem Statement · Editorial Solution

  • Min Heap

    Problem Statement · Editorial Solution

  • Min Max Stack

    Problem Statement · Editorial Solution

  • Molecular Reactor Queue

    Problem Statement · Editorial Solution

  • Moving Average from Data Stream

    Problem Statement · Editorial Solution

  • Moving Average Without Top-K

    Problem Statement · Editorial Solution

  • Multi-Currency Wallet

    Problem Statement · Editorial Solution

  • Multiplayer Chess Game

    Problem Statement · Editorial Solution

  • Music Streaming App

    Problem Statement · Editorial Solution

  • My Calendar I

    Problem Statement · Editorial Solution

  • N Stacks in a Single Array

    Problem Statement · Editorial Solution

  • Nested Comment Service

    Problem Statement · Editorial Solution

  • Notepad System

    Problem Statement · Editorial Solution

  • Notification Factory

    Problem Statement · Editorial Solution

  • Number of Recent Calls

    Problem Statement · Editorial Solution

  • Observer Pattern - Notification System

    Problem Statement · Editorial Solution

  • On-Device AI Feature Cache

    Problem Statement · Editorial Solution

  • Order Book - Matching Engine

    Problem Statement · Editorial Solution

  • Ordered Logger

    Problem Statement · Editorial Solution

  • Payment Ledger

    Problem Statement · Editorial Solution

  • Payment Module with Strategy Pattern

    Problem Statement · Editorial Solution

  • Payment Planner / Subscription Logic

    Problem Statement · Editorial Solution

  • Payment Processor State Machine

    Problem Statement · Editorial Solution

  • Payment Scheduler

    Problem Statement · Editorial Solution

  • Payment Terminal

    Problem Statement · Editorial Solution

  • Payment Wallet System

    Problem Statement · Editorial Solution

  • Peeking Iterator

    Problem Statement · Editorial Solution

  • Permissions and Sharing System

    Problem Statement · Editorial Solution

  • Physician Consultation Queuing Application

    Problem Statement · Editorial Solution

  • Pin and Board Management Service

    Problem Statement · Editorial Solution

  • Playlist Management with Doubly Linked List

    Problem Statement · Editorial Solution

  • Pokemon Trade Application

    Problem Statement · Editorial Solution

  • Predictive Battery Management System

    Problem Statement · Editorial Solution

  • Print in Order

    Problem Statement · Editorial Solution

  • Prioritized Job Queue with Retries

    Problem Statement · Editorial Solution

  • QuadTree Logic / Spatial Indexing

    Problem Statement · Editorial Solution

  • Radar Data Pipeline

    Problem Statement · Editorial Solution

  • Range Module

    Problem Statement · Editorial Solution

  • Ranked Cache System

    Problem Statement · Editorial Solution

  • Rate Limiting Function (Throttle)

    Problem Statement · Editorial Solution

  • Rating & Review System

    Problem Statement · Editorial Solution

  • Real-Time Currently Watching Tracker

    Problem Statement · Editorial Solution

  • Real-Time Event Ingestion and Statistics

    Problem Statement · Editorial Solution

  • Real-Time Top K Players Leaderboard

    Problem Statement · Editorial Solution

  • Recommendation Engine

    Problem Statement · Editorial Solution

  • Rectangle Fit Check

    Problem Statement · Editorial Solution

  • Request Replaying / Idempotency

    Problem Statement · Editorial Solution

  • Resource Loader

    Problem Statement · Editorial Solution

  • Restaurant Booking System

    Problem Statement · Editorial Solution

  • Restaurant Order Queue

    Problem Statement · Editorial Solution

  • Resume Search System

    Problem Statement · Editorial Solution

  • Review Workflow State Machine

    Problem Statement · Editorial Solution

  • Ride Sharing Service

    Problem Statement · Editorial Solution

  • Ring Buffer for Producer-Consumer

    Problem Statement · Editorial Solution

  • Risk Control Kill Switch

    Problem Statement · Editorial Solution

  • Rock Paper Scissors

    Problem Statement · Editorial Solution

  • Sales Tax Calculator

    Problem Statement · Editorial Solution

  • Scooter State Machine

    Problem Statement · Editorial Solution

  • Search URL Builder

    Problem Statement · Editorial Solution

  • Secure Token Management

    Problem Statement · Editorial Solution

  • Self-Balancing BST

    Problem Statement · Editorial Solution

  • Sensor Data Aggregator

    Problem Statement · Editorial Solution

  • Server Load Balancer

    Problem Statement · Editorial Solution

  • Shopping Cart

    Problem Statement · Editorial Solution

  • Simplified Block Editor

    Problem Statement · Editorial Solution

  • Simplified Version Control System

    Problem Statement · Editorial Solution

  • Simulation Scenario Runner

    Problem Statement · Editorial Solution

  • Sliding Window

    Problem Statement · Editorial Solution

  • Smallest Number in Infinite Set

    Problem Statement · Editorial Solution

  • Smart Pointer (Shared Pointer with Reference Counting)

    Problem Statement · Editorial Solution

  • Snake and Ladder Game

    Problem Statement · Editorial Solution

  • Snapchat Ephemeral Messaging System

    Problem Statement · Editorial Solution

  • Snapshot Array

    Problem Statement · Editorial Solution

  • Snapshot Set with Iterator

    Problem Statement · Editorial Solution

  • Song Playlist

    Problem Statement · Editorial Solution

  • Sparse Matrix Multiplication

    Problem Statement · Editorial Solution

  • Splitwise (Expense Sharing)

    Problem Statement · Editorial Solution

  • Stock Price Fluctuation

    Problem Statement · Editorial Solution

  • Stock Price Tracker (Observer Pattern)

    Problem Statement · Editorial Solution

  • Stock Trading System with User Validation

    Problem Statement · Editorial Solution

  • Surge Pricing Validator

    Problem Statement · Editorial Solution

  • Tennis Game Score Tracker

    Problem Statement · Editorial Solution

  • Thread-Safe Account Ledger

    Problem Statement · Editorial Solution

  • Thread-Safe Shared Counter

    Problem Statement · Editorial Solution

  • Thread-Safe Singleton

    Problem Statement · Editorial Solution

  • Three Stacks in One Array

    Problem Statement · Editorial Solution

  • Ticketmaster-like Concurrent Booking System

    Problem Statement · Editorial Solution

  • Time Based Key-Value Store

    Problem Statement · Editorial Solution

  • Token Bucket

    Problem Statement · Editorial Solution

  • Top K Frequent Elements Stream

    Problem Statement · Editorial Solution

  • Traffic Signal Controller

    Problem Statement · Editorial Solution

  • Train Platform Management System

    Problem Statement · Editorial Solution

  • Transaction Aggregator: Highest Volume Merchant

    Problem Statement · Editorial Solution

  • Transaction Categorization Service

    Problem Statement · Editorial Solution

  • Transaction History Service

    Problem Statement · Editorial Solution

  • Transaction Parser / Ledger

    Problem Statement · Editorial Solution

  • Transaction Processing Engine

    Problem Statement · Editorial Solution

  • Transaction Service

    Problem Statement · Editorial Solution

  • Transaction State Machine

    Problem Statement · Editorial Solution

  • Transaction Statistics

    Problem Statement · Editorial Solution

  • Transaction Store

    Problem Statement · Editorial Solution

  • Transactional Key-Value Store with Nested Transactions

    Problem Statement · Editorial Solution

  • Truck Tracking System

    Problem Statement · Editorial Solution

  • Tweet Counts Per Frequency

    Problem Statement · Editorial Solution

  • Two Sum III - Data structure design

    Problem Statement · Editorial Solution

  • Undo Redo System

    Problem Statement · Editorial Solution

  • Undo/Redo for Spreadsheet

    Problem Statement · Editorial Solution

  • URL Shortener

    Problem Statement · Editorial Solution

  • User Token Credit Tracker

    Problem Statement · Editorial Solution

  • Utility Payment Interface

    Problem Statement · Editorial Solution

  • Vending Machine

    Problem Statement · Editorial Solution

  • Vending Machine for Hotels

    Problem Statement · Editorial Solution

  • Vesting Schedule Domain Model

    Problem Statement · Editorial Solution

  • Violation Log Analyzer

    Problem Statement · Editorial Solution

  • Window Management System

    Problem Statement · Editorial Solution

  • Windowed Average Cache

    Problem Statement · Editorial Solution

  • Word Guessing Game

    Problem Statement · Editorial Solution