Low Level System Design

Account Balance Tracker

Building Interface: Hospital and School

Coffee Shop Decorator

Cookie Manager

Go Fish (Card Game)

Implement Queue using Array

Implement Queue using Stacks

Implement Stack Using Arrays

Implement Stack using Queues

In-Memory Key-Value CRUD Store

Moving Average from Data Stream

Notification Factory

Number of Recent Calls

Print in Order

Rock Paper Scissors

Shopping Cart

Two Sum III - Data structure design

2048 Game Implementation

Access Control Tree

Account Management Service

Active Users in N Minutes

Actor Component Model

AirMap Route Finder

API Billing & Usage System

ASCII Canvas - Draw Rectangle

Async: Limit (Concurrency Control)

AsyncTaskQueue (Concurrency Control)

Autocomplete Utility

Avatar Component Loading Order

Background Job Processor with Retries

Banking Application

Banking Operations Debugging

Banking System (Progressive)

Banking System API

Basic Blockchain

Batching Utility with Timeout

Battleship Game Simulation

Bet Placement Ledger with Idempotent Settlement

Betting Slip with Accumulator and Each-Way Returns

Bookstore Word Counter

Browser History Data Structure

Buffered File System

Buffered File Writer

Burger Shop (Builder Pattern)

Candidate Recruiter Management System

Card Transaction Authorization System

Cargo Shipping Calculator

CD With Symbolic Links

Chat Profanity Filter

Circuit Breaker

Circular Buffer

Comment Threading Model

Component Design: Virtualized List

Concurrent Money Transfer

Configuration Rules SDK with Rule Precedence

Connect 4 Backend

Connect Four

Coupon Redemption System

Credit Tracker with Expirations

Critical Memory Alert Analysis

Custom Dynamic Array

Custom Playlist Picture System

Customer Support Leaderboard

DAG Task Graph

Data Source Difference Tracker

DataStream Guessing Game

Debounced Search Bar

Decorator Pattern Tax/Discount Calculator

Deep Copy Manager

Delayed Payment System

Design a 3D Binary Matrix with Efficient Layer Tracking

Design a Bank Account Class

Design a Credit Card Limit Manager

Design a Credit Tracker

Design A Leaderboard

Design a Logging Library

Design a Rate Limiter for an AI Hub

Design a Specialized Cache

Design a Stack with Increment Operation

Design a Todo List

Design an Anagram Store

Design an ATM System

Design an Elevator Dispatcher

Design an ID Allocator

Design Browser History

Design Circular Deque

Design Circular Queue

Design File System

Design File System Find API

Design Linked List

Design Log Parser

Design Log Storage System

Design Playlist Data Structure

Design Retriable Function

Design Spreadsheet With Undo Redo

Design Tic-Tac-Toe

Design Underground System

Detect Squares

Disk Space Manager

Document Version Control System

Driver-Order Matching System

Elevator System

Encode and Decode TinyURL

Event Emitter

Expandable Array Implementation

Fault-Tolerant Redis Wrapper

File Collections Tracker

File Storage Query System

File Tree Management

Find Consecutive Integers from a Data Stream

First Unique Number

Flatten Nested List Iterator

Flight Booking System

Fractional Share Inventory

Fraud Detection: Rolling Window Thresholds

Frequency Tracker

Game Lobby State Machine

Graph Implementation

Growing List (Dynamic Array)

Handling Concurrent Credit Deductions

Hash Table Implementation

Hierarchical Menu Price

High Frequency Sensor Data Aggregator

Hotel CRUD & Proximity Search

Idempotent Payment Processor

Immutable Class Implementation

Implementing Core Linux Commands

In-Memory Ledger

In-Memory Load Balancer

Input Remapping System

Insurance Policy Logic Engine

Inventory and Item System

Inventory Manager

Jigsaw Puzzle Solver

K-Way Merge Iterator

Key Generation Service

KV Store with Sliding Window QPS

Lightweight Load Balancer

Live Odds Market Board

Loan State Machine

Locker Allocation System

Log Monitoring and Alerting System

Logger Rate Limiter

LRU Cache with Serialization

Mars Rover

Meeting Room Reservation System

Meeting Scheduler

Memory Efficient Circular Frame Buffer

Message Buffer with Flush Policy

Micro-Deposit Verification

Min Heap

Min Max Stack

Molecular Reactor Queue

Multiplayer Chess Game

Music Streaming App

My Calendar I

Nested Comment Service

Notepad System

Observer Pattern - Notification System

On-Device AI Feature Cache

Ordered Logger

Payment Ledger

Payment Module with Strategy Pattern

Payment Planner / Subscription Logic

Payment Processor State Machine

Payment Scheduler

Payment Terminal

Payment Wallet System

Peeking Iterator

Permissions and Sharing System

Physician Consultation Queuing Application

Playlist Management with Doubly Linked List

Pokemon Trade Application

Predictive Battery Management System

QuadTree Logic / Spatial Indexing

Radar Data Pipeline

Range Module

Ranked Cache System

Rate Limiting Function (Throttle)

Rating & Review System

Real-Time Top K Players Leaderboard

Recommendation Engine

Rectangle Fit Check

Request Replaying / Idempotency

Resource Loader

Restaurant Booking System

Restaurant Order Queue

Review Workflow State Machine

Ring Buffer for Producer-Consumer

Sales Tax Calculator

Scooter State Machine

Search URL Builder

Secure Token Management

Server Load Balancer

Simplified Block Editor

Smallest Number in Infinite Set

Smart Pointer (Shared Pointer with Reference Counting)

Snake and Ladder Game

Snapshot Array

Song Playlist

Sparse Matrix Multiplication

Stock Price Fluctuation

Stock Price Tracker (Observer Pattern)

Stock Trading System with User Validation

Surge Pricing Validator

Tennis Game Score Tracker

Thread-Safe Account Ledger

Thread-Safe Shared Counter

Thread-Safe Singleton

Ticketmaster-like Concurrent Booking System

Time Based Key-Value Store

Top K Frequent Elements Stream

Traffic Signal Controller

Train Platform Management System

Transaction Aggregator: Highest Volume Merchant

Transaction Categorization Service

Transaction History Service

Transaction Parser / Ledger

Transaction Processing Engine

Transaction Service

Transaction State Machine

Transaction Statistics

Transaction Store

Truck Tracking System

Tweet Counts Per Frequency

Undo Redo System

Undo/Redo for Spreadsheet

URL Shortener

User Token Credit Tracker

Utility Payment Interface

Vending Machine for Hotels

Violation Log Analyzer

Window Management System

Word Guessing Game

2D Vector Class

Alerting Engine Rules

All O`one Data Structure

API Rate Limiter

Caching Library with Pluggable Eviction Policies

Central Banking Ledger

Cloud Billing System

Cloud Storage

Column Index

Container Orchestrator

Credit-Based Purchase Model

Custom HashMap with Bulk Operations

Data Stream as Disjoint Intervals

Design 3 Stacks in 1 Array

Design a Tetris Game

Design a Text Editor

Design an Expression Tree With Evaluate Function

Design BigInteger

Design GPU Credits

Design Hit Counter

Design In-Memory Database

Design In-Memory File System

Design Search Autocomplete System

Design Skip List

Dinner Plate Stacks

Distributed Lock Manager

Financial Ledger (Double-Entry Accounting)

Financial Stream Processing

Food Delivery Matching Engine

Frequency and Distance Top-K Query System

Gameplay Ability System

iCloud Photo Sync with Conflict Resolution

Idempotent Transaction Ledger

In-Memory Banking System

In-Memory Cloud Storage with Quotas

In-Memory Database

In-Memory Message Broker

Insert Delete GetRandom O(1) - Duplicates allowed

Inventory Management System

Key-Value Store with TTL and Transactions

Lazy Update Priority Queue

Library Management System

Log Collection and Aggregation System

Log Parser Rolling Average Storage

Log-Query Stream Processor

Max Stack

Maximum Frequency Stack

Memory Allocator

Message Processing System

Movie Ticket Booking System

Moving Average Without Top-K

Multi-Currency Wallet

N Stacks in a Single Array

Order Book - Matching Engine

Pin and Board Management Service

Prioritized Job Queue with Retries

Real-Time Currently Watching Tracker

Real-Time Event Ingestion and Statistics

Resume Search System

Ride Sharing Service

Risk Control Kill Switch

Self-Balancing BST

Sensor Data Aggregator

Simplified Version Control System

Simulation Scenario Runner

Sliding Window

Snapchat Ephemeral Messaging System

Snapshot Set with Iterator

Splitwise (Expense Sharing)

Three Stacks in One Array

Token Bucket

Transactional Key-Value Store with Nested Transactions

Vending Machine

Vesting Schedule Domain Model