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Master Systems Through Hands-On Practice

Whether you are preparing for your first system design round or leveling up to senior, practice with interactive simulations, structured steps, and AI feedback.

Start Exploring 🎨 Free Canvas

From your first HLD to staff-level tradeoffs — practice at your level

8 free starter problems47 simulationsAI step-by-step practiceFree canvas
Launching today — try it free, feedback welcome

Simulation is the New Learning

Don't just read about distributed systems. Break them. Fix them. Optimize them. Our interactive widgets let you experience the trade-offs firsthand.

⚡️ Handle the thundering herd

Simulate millions of users competing for limited inventory. Learn race conditions, locking strategies, and queueing.

Flash Sale System
Simulate 150 users fighting for 100 items. Toggle Locking to prevent overselling.
100
Stock Left

Virtual Queue

0 Waiting

Sales Processed

0 Sold
0/100 Sold

🔒 Secure by Design

Visualize encryption, key management, and secure storage implementation details.

Secret Vault

Centralized secret storage. No hardcoded creds.

LOCKED
My Application
Secrets are never stored in code. Apps authenticate (e.g., via IAM) and request a short-lived lease for the secret.

🔌 API First Engineering

Master GraphQL and REST patterns. Understand schemas, resolvers, and over-fetching issues visually.

  • Interactive Schema Explorer
  • Query Builder
  • Real-time Response Validation

GraphQL Playground

Ask for exactly what you need. No over-fetching.

query GetUser {
user(id: "1") {
}
}
Construct query and press Run
Notice how the server returns only the requested fields. This solves the "Over-fetching" problem common in REST.

Structured Learning Paths

Not sure where to start? Follow our carefully curated roadmaps tailored for different engineering roles. From Junior to Staff Engineer, we have a path for you.

Software Engineer

Master the fundamentals of scalable web apps.

Start Path

Senior SE

Deep dive into distributed systems patterns.

Start Path

MLOps & MLE

Deploying and scaling machine learning models.

Start Path

Agentic AI

Building autonomous agent orchestrators.

Start Path
Most asked interviews

Popular at top companies

Curated problem sets frequently asked in system design loops. Select a company to filter the library below.

Start Practicing

Pick a real-world problem and start designing. Master the patterns used by top tech companies.

Easy
Design TinyURL

A URL shortening service like bit.ly. Handle 100M redirects/day.

ID GenerationHashingCachingAnalytics
AmazonGoogle
Basics
Practice
ProMedium
Design YouTube

Video streaming platform with recommendations and real-time comments.

StreamingCDNMachine LearningVideo
NetflixYouTube
Core Services
Unlock
ProMedium
Design Twitter

Real-time social media platform for tweets and follows.

Fan-out on WriteSocial FeedReal-timeCaching
TwitterMeta
Core Services
Unlock
ProMedium
Design Instagram

Photo sharing with stories and reels.

Object StorageCDNSocial FeedMachine Learning
MetaSnapchat
Core Services
Unlock
ProHard
Design Uber

Ride-sharing with real-time matching and ETA.

GeospatialReal-timeMatchingPayments
UberLyft
Core Services
Unlock
ProHard
Design Netflix

Video streaming with personalized recommendations.

StreamingCDNMachine LearningVideo
NetflixAmazon
Core Services
Unlock
Medium
Design WhatsApp

Real-time messaging with end-to-end encryption.

MessagingEncryptionReal-timePub/Sub
MetaSignal
Core Services
Practice
ProHard
Design Facebook News Feed

Algorithmic feed with posts from friends and pages.

Fan-out on WriteSocial FeedCachingMachine Learning
MetaLinkedIn
Advanced
Unlock
ProHard
Design Google Search

Web search with indexing and ranking.

Inverted IndexWeb CrawlingSearch & RankingTypeahead
GoogleBing
Advanced
Unlock
Medium
Design Dropbox

File storage and synchronization across devices.

Sync & ConflictObject StorageChunkingReplication
DropboxGoogle Drive
Core Services
Practice
Easy
Design a Parking Lot System

Automated parking with entry/exit management.

OOP DesignState MachineScheduling
Local Systems
Basics
Practice
Medium
Design an Elevator System

Multi-floor elevator control system.

OOP DesignState MachineScheduling
Building Systems
Basics
Practice
Hard
Design a Distributed Cache (Redis-like)

In-memory data store with replication.

CachingConsistent HashingReplicationEviction Policies
Redis LabsAmazon
Advanced
Practice
Medium
Design a Typeahead Suggestion

Autocomplete for search queries.

TypeaheadCachingSearch & Ranking
GoogleAmazon
Advanced
Practice
Medium
Design a Unique ID Generator

Generate unique IDs at scale.

ID GenerationShardingConsensus
Basics
Practice
ProMedium
Design a Leaderboard

Real-time ranking system.

Real-timeCachingAnalytics
GamingSports
Edge Cases
Unlock
ProMedium
Design a Rate Limiter

Limit requests per user/time.

Rate LimitingKey-Value StoreCaching
API Providers
Edge Cases
Unlock
ProHard
Design a Recommendation Engine

Personalized content recommendations.

Machine LearningData PipelineAnalytics
NetflixAmazon
ML-Infused
Unlock
ProHard
Design Fraud Detection System

Detect fraudulent transactions.

Machine LearningReal-timeAnalyticsPayments
PayPalStripe
ML-Infused
Unlock
ProHard
Design Personalized Search Ranking

Search results tailored to user.

Search & RankingMachine LearningInverted Index
GoogleBing
ML-Infused
Unlock
ProMedium
Design A/B Testing Framework

Experimentation platform for features.

AnalyticsExperimentationData Pipeline
GoogleMeta
Edge Cases
Unlock
ProMedium
Design a Notification System

Push notifications with scheduling.

NotificationsPub/SubFan-out on Write
SlackGmail
Core Services
Unlock
ProMedium
Design a File Storage System

Cloud storage with versioning.

Object StorageReplicationSync & ConflictMetadata
AWS S3Google Drive
Core Services
Unlock
ProHard
Design a Task Scheduler

Distributed job scheduling.

SchedulingMessage QueueLeader Election
AirflowKubernetes
Advanced
Unlock
ProHard
Design a Video Call System

Real-time video conferencing.

Real-timeStreamingWebSocketsVideo
ZoomGoogle Meet
Advanced
Unlock
ProMedium
Design a Logging System

Centralized log aggregation.

ObservabilityAnalyticsSearch & Ranking
ELK StackSplunk
Basics
Unlock
ProMedium
Design a Metrics Monitoring System

System metrics collection and visualization.

ObservabilityAnalyticsTime Series
PrometheusGrafana
Basics
Unlock
ProMedium
Design a Key-Value Store

Distributed key-value database.

Key-Value StoreShardingReplicationConsistency
RedisDynamoDB
Advanced
Unlock
ProMedium
Design a Message Queue

Asynchronous message processing.

Message QueuePub/SubReplication
KafkaRabbitMQ
Core Services
Unlock
ProMedium
Design a Load Balancer

Distribute traffic across servers.

Load BalancerHealth ChecksCaching
AWS ELBNGINX
Basics
Unlock
ProHard
Design a CDN

Content delivery network.

CDNCachingGeospatial
CloudflareAkamai
Advanced
Unlock
ProMedium
Design a Web Crawler

Crawl and index web pages.

Web CrawlingSchedulingDistributed FS
GoogleBing
Advanced
Unlock
ProHard
Design a Distributed File System

Store files across multiple nodes.

Distributed FSReplicationMetadata
HDFSCeph
Advanced
Unlock
ProHard
Design a Leader Election System

Elect a leader in distributed systems.

Leader ElectionConsensusDistributed FS
ZooKeeperetcd
Advanced
Unlock
ProMedium
Design a Configuration Management System

Manage application configurations.

API DesignReplicationRollout
ConsulSpring Cloud Config
Basics
Unlock
ProMedium
Design a Secret Management System

Store and manage secrets securely.

EncryptionSecurityCompliance
VaultAWS Secrets Manager
Basics
Unlock
ProMedium
Design a CI/CD Pipeline

Continuous integration and deployment.

DeploymentAutomationAPI Design
JenkinsGitLab CI
Basics
Unlock
ProHard
Design a Microservices Architecture

Break down monolithic app into services.

API DesignService MeshEvent-Driven
NetflixUber
Advanced
Unlock
ProMedium
Design a GraphQL API

Flexible API with schema.

API DesignCachingAPI Gateway
GitHubShopify
Core Services
Unlock
ProEasy
Design a REST API

RESTful web service.

API DesignRate LimitingSecurity
TwitterGitHub
Basics
Unlock
ProMedium
Design a WebSocket System

Real-time bidirectional communication.

WebSocketsReal-timePub/Sub
SlackDiscord
Core Services
Unlock
ProHard
Design a Collaborative Editor

Real-time document editing.

CRDT / OTReal-timeSync & Conflict
Google DocsNotion
Advanced
Unlock
ProHard
Design an Ad Serving System

Serve ads with targeting.

Ad ServingAuctionReal-timeMachine Learning
Google AdsMeta Ads
Advanced
Unlock
ProHard
Design a Personalized Feed

Tailored content feed.

Social FeedMachine LearningCachingSearch & Ranking
TikTokInstagram
ML-Infused
Unlock
ProMedium
Design a Feature Flag System

Toggle features dynamically.

RolloutAPI DesignCaching
LaunchDarklySplit
Basics
Unlock
ProHard
Design a Service Mesh

Manage service-to-service communication.

Service MeshObservabilitySecurity
IstioLinkerd
Advanced
Unlock
ProMedium
Design a Distributed Tracing System

Trace requests across services.

ObservabilityAnalyticsService Mesh
JaegerZipkin
Advanced
Unlock
ProMedium
Design a Compliance Auditing System

Audit for regulatory compliance.

ComplianceAnalyticsEncryption
Compliance tools
Basics
Unlock
ProMedium
Design a GDPR Compliant System

Data privacy and compliance.

ComplianceEncryptionData Pipeline
EU regulations
Basics
Unlock
ProHard
Design a Blockchain System

Decentralized ledger.

ConsensusReplicationEncryption
BitcoinEthereum
Advanced
Unlock
ProHard
Design an IoT Platform

Manage Internet of Things devices.

IoTPub/SubAnalyticsReal-time
AWS IoTGoogle IoT
Advanced
Unlock
ProHard
Design an AR/VR System

Augmented/Virtual reality platform.

StreamingReal-timeVideo
OculusMagic Leap
Advanced
Unlock
ProHard
Design a Quantum Computing System

Harness quantum mechanics for computation.

SchedulingDistributed FS
IBM QuantumGoogle Quantum
Advanced
Unlock
ProHard
Design a Metaverse Platform

Virtual shared space.

Real-timeSync & ConflictObject Storage
MetaDecentraland
Advanced
Unlock
ProHard
Design a Brain-Computer Interface

Direct brain-to-computer communication.

Real-timeStreamingAnalytics
NeuralinkKernel
Advanced
Unlock
ProMedium
Design a Space Debris Tracking System

Track and manage space junk.

GeospatialReal-timeAnalytics
NASAESA
Edge Cases
Unlock
ProHard
Design a Personalized Learning Platform

Adaptive education system.

Machine LearningAnalyticsRecommendations
CourseraKhan Academy
ML-Infused
Unlock
ProHard
Design a Climate Model Simulator

Simulate climate change.

Data PipelineAnalyticsBatch Processing
NOAAIPCC
ML-Infused
Unlock
ProHard
Design a Global Supply Chain Optimizer

Optimize logistics worldwide.

AnalyticsSchedulingGraph Algorithms
DHLAmazon
Advanced
Unlock
ProMedium
Design a Zero-Trust Network

Security model with no implicit trust.

SecurityEncryptionAPI Gateway
GoogleMicrosoft
Basics
Unlock
ProMedium
Design a Carbon Footprint Tracker

Track environmental impact.

AnalyticsData PipelineIoT
Green tech
Edge Cases
Unlock
ProMedium
Design a Sustainable Data Center

Energy-efficient computing infrastructure.

AnalyticsSchedulingIoT
GoogleMicrosoft
Basics
Unlock
ProHard
Design a Federated Learning System

Train ML models without sharing data.

Machine LearningEncryptionDistributed FS
GoogleApple
ML-Infused
Unlock
ProHard
Design an Explainable AI System

Make AI decisions interpretable.

Machine LearningAnalyticsCompliance
OpenAIGoogle
ML-Infused
Unlock
ProMedium
Design a Vector Database

Store and query vector embeddings.

Vector DBSearch & RankingIndexing
PineconeWeaviate
Advanced
Unlock
ProHard
Design a Multi-Modal Search Engine

Search across text, images, audio.

Search & RankingMachine LearningVector DB
GoogleBing
ML-Infused
Unlock
ProHard
Design an Autonomous Agent Orchestrator

Coordinate AI agents.

AI AgentsLLMOrchestration
OpenAIAnthropic
Advanced
Unlock
ProHard
Design a Generative AI Content Moderator

Moderate AI-generated content.

Content ModerationMachine LearningLLM
OpenAIStability AI
ML-Infused
Unlock
ProHard
Design a RAG System

Retrieval-Augmented Generation.

RAGVector DBLLM
LangChainPinecone
ML-Infused
Unlock
ProHard
Design a Conversational AI Platform

Build chatbots and virtual assistants.

LLMReal-timeMessaging
DialogflowRasa
ML-Infused
Unlock
ProHard
Design a Real-Time Analytics System

Process and analyze streaming data.

AnalyticsStream ProcessingReal-time
SnowflakeDatabricks
Advanced
Unlock
ProMedium
Design a Data Lake

Store diverse data for analytics.

Data PipelineObject StorageETL
AWSAzure
Advanced
Unlock
ProMedium
Design a Data Warehouse

Centralized data repository.

ETLAnalyticsData Pipeline
RedshiftBigQuery
Advanced
Unlock
ProMedium
Design a ETL Pipeline

Extract, Transform, Load data.

ETLData PipelineScheduling
TalendInformatica
Basics
Unlock
ProMedium
Design a Backup and Recovery System

Ensure data durability.

ReplicationObject StorageHigh Availability
VeeamCommvault
Basics
Unlock
ProHard
Design a Disaster Recovery System

Recover from catastrophic failures.

High AvailabilityReplicationFailover
AWS DRAzure DR
Advanced
Unlock
ProHard
Design a High-Availability System

Minimize downtime.

High AvailabilityReplicationLoad Balancer
NetflixAmazon
Advanced
Unlock
ProMedium
Design a Scalable API Gateway

Manage API traffic.

API GatewayRate LimitingLoad Balancer
KongApigee
Core Services
Unlock
ProMedium
Design a Event-Driven Architecture

Decouple services with events.

Event-DrivenPub/SubMessage Queue
EventbriteStripe
Advanced
Unlock
ProHard
Design a Saga Pattern Implementation

Manage distributed transactions.

SagaEvent-DrivenIdempotency
Microservices patterns
Advanced
Unlock
ProMedium
Design a Circuit Breaker Pattern

Prevent cascading failures.

Circuit BreakerResilienceObservability
Netflix Hystrix
Basics
Unlock
ProMedium
Design a Strangler Fig Migration

Migrate legacy systems incrementally.

Strangler FigAPI GatewayEvent-Driven
Migration strategies
Basics
Unlock
ProMedium
Design a Blue-Green Deployment

Zero-downtime deployments.

Blue-Green DeployDeploymentHigh Availability
Deployment strategies
Basics
Unlock
ProHard
Design a Flash Sale System

High concurrency ticket booking.

E-commerceCachingRate LimitingInventory
TicketmasterAmazon
Advanced
Unlock
ProHard
Design a Payment System

Financial transaction processing.

PaymentsIdempotencyConsistencySecurity
StripePayPal
Core Services
Unlock
ProMedium
Design an LRU Cache

Design a Least Recently Used (LRU) Cache mechanism.

CachingData Structures
GoogleAmazonMeta
Basics
Unlock

Ready to Design?

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