System Design
Design Playgrounds
Rehearse distributed architectures. Analyze component topologies, run metric simulations, and run chaos experiments on real-world system patterns.
Design Ad Click Aggregation
Design a real-time ad click aggregation system that counts ad clicks per minute/hour, detects fraud, and provides query capabilities for billing and analytics at scale.
- Hard Complexity
- Interactive Canvas Playground
Design AI Chatbot
Design a ChatGPT-style conversational AI service: users send messages, the system streams back model-generated responses while preserving multi-turn conversation context.
- Intermediate Complexity
- Interactive Canvas Playground
Design Cache Layer
Design and implement a caching layer for a high-traffic web application, covering cache strategies, eviction policies, invalidation, and cache stampede prevention.
- Intermediate Complexity
- Interactive Canvas Playground
Design Chat System
Design a real-time messaging system like WhatsApp or Slack that supports 1-to-1 messaging, group chats, message delivery guarantees, and online presence.
- Intermediate Complexity
- Interactive Canvas Playground
Design Distributed Key-Value Store
Design a distributed key-value store like Amazon DynamoDB or Apache Cassandra that provides high availability, horizontal scalability, and tunable consistency.
- Hard Complexity
- Interactive Canvas Playground
Design E-Commerce Platform
Design an e-commerce platform like Amazon that handles product catalog, inventory management, shopping cart, checkout, and order fulfillment at massive scale.
- Hard Complexity
- Interactive Canvas Playground
Design FB Post Search
Design a search system for a social platform (like Facebook) that allows users to search posts, people, pages, and groups with results filtered by their social graph and privacy settings.
- Intermediate Complexity
- Interactive Canvas Playground
Design Food Delivery (Swiggy)
Design a food delivery platform like Swiggy or DoorDash where users browse restaurants, place orders, and track delivery in real-time, while managing restaurant menus, availability, and dynamic delivery pricing.
- Hard Complexity
- Interactive Canvas Playground
Design Full Production Stack
Design a complete production-ready infrastructure stack for a large-scale web application, covering all layers: CDN, API gateway, microservices, data stores, observability, and CI/CD.
- Hard Complexity
- Interactive Canvas Playground
Design Google Docs
Design a collaborative document editor like Google Docs where multiple users can edit the same document simultaneously with real-time updates and conflict resolution.
- Hard Complexity
- Interactive Canvas Playground
Design Google Drive / Dropbox
Design a cloud file storage service like Google Drive or Dropbox where users can upload, sync, share, and collaborate on files across multiple devices.
- Hard Complexity
- Interactive Canvas Playground
Design Instagram
Design Instagram — a photo and video sharing platform where users post content, follow others, see a personalized feed, and interact via likes, comments, and stories.
- Intermediate Complexity
- Interactive Canvas Playground
Design Live Streaming (Twitch)
Design a live streaming platform like Twitch where content creators broadcast in real-time to potentially millions of concurrent viewers with low latency, while supporting live chat and reactions.
- Hard Complexity
- Interactive Canvas Playground
Design LLM Serving Platform
Design a platform that serves self-hosted LLMs at scale on a GPU fleet — maximizing throughput (tokens/sec) and GPU utilization while keeping tail latency low, like a vLLM/Triton-based inference service.
- Hard Complexity
- Interactive Canvas Playground
Design Message Queue
Design a message queue system like Apache Kafka or Amazon SQS that enables asynchronous communication between services with guaranteed delivery, at-least-once semantics, and consumer group support.
- Intermediate Complexity
- Interactive Canvas Playground
Design Monitoring / Metrics (Datadog)
Design a metrics monitoring and alerting system like Datadog or Prometheus that collects time-series metrics from thousands of services, stores them efficiently, and triggers alerts on threshold violations.
- Hard Complexity
- Interactive Canvas Playground
Design Notification System
Design a notification system that delivers messages via push (iOS/Android), email, and SMS to 100M+ users with reliable delivery, deduplication, and user preference management.
- Intermediate Complexity
- Interactive Canvas Playground
Design Online Judge (LeetCode)
Design an online code judge like LeetCode or HackerRank where users submit code solutions, which are compiled and executed in a sandboxed environment against test cases, returning results within seconds.
- Intermediate Complexity
- Interactive Canvas Playground
Design Pastebin
Design a text-sharing service like Pastebin where users can paste text/code and share it via a short URL, with optional expiry, syntax highlighting, and access control.
- Intermediate Complexity
- Interactive Canvas Playground
Design RAG System
Design a Retrieval-Augmented Generation system: ground an LLM's answers in your own corpus so it cites real sources and avoids hallucination — e.g. an enterprise knowledge assistant.
- Hard Complexity
- Interactive Canvas Playground
Design Rate Limiter (Standalone)
Design a rate limiter that can enforce configurable request rate limits per user, IP, or API key, across a distributed fleet of servers, with low latency impact.
- Intermediate Complexity
- Interactive Canvas Playground
Design Recommendation System
Design a large-scale recommendation system (feed/products/video) that selects, from millions of items, the handful a user is most likely to engage with — in tens of milliseconds.
- Hard Complexity
- Interactive Canvas Playground
Design Ride-Sharing Platform
Design a ride-sharing platform like Uber or Lyft that matches riders to nearby drivers in real-time, handles dynamic pricing (surge), and tracks trips end-to-end.
- Hard Complexity
- Interactive Canvas Playground
Design Semantic Search
Design a semantic search engine that retrieves documents by meaning, not just keywords — e.g. "how do I cancel my plan" matches "subscription termination steps".
- Intermediate Complexity
- Interactive Canvas Playground
Design Simple Web App
Design the foundational architecture for a scalable web application that can serve millions of users with high availability, starting from a single server and scaling out.
- Intermediate Complexity
- Interactive Canvas Playground
Design Social Media Feed
Design the news feed system for a social platform like Twitter/X or Facebook where users see posts from people they follow, in reverse-chronological or ranked order.
- Hard Complexity
- Interactive Canvas Playground
Design Stock Trading System
Design a stock trading platform like Robinhood or Zerodha that processes buy/sell orders with a matching engine, provides real-time price feeds, and maintains a persistent order book.
- Hard Complexity
- Interactive Canvas Playground
Design Ticket Booking (BookMyShow)
Design a ticket booking system like BookMyShow or Ticketmaster where users can browse events, select seats, and purchase tickets with guaranteed no double-booking under high concurrency.
- Intermediate Complexity
- Interactive Canvas Playground
Design Tinder
Design a swipe-based dating app like Tinder where users are shown profiles of nearby people, can swipe right (like) or left (pass), and are matched when both swipe right.
- Intermediate Complexity
- Interactive Canvas Playground
Design Type-Ahead Search
Design a type-ahead (autocomplete) search system like Google's search bar that suggests completions as users type, ranked by relevance and popularity, with < 100ms response time.
- Intermediate Complexity
- Interactive Canvas Playground
Design UPI Payment Gateway
Design a UPI-based payment system like Google Pay or PhonePe that handles instant bank-to-bank transfers, handles 1B+ transactions per day, and ensures zero double spends.
- Hard Complexity
- Interactive Canvas Playground
Design URL Shortener
Design a service like bit.ly that converts long URLs into short, unique aliases and redirects users to the original URL when visited.
- Intermediate Complexity
- Interactive Canvas Playground
Design Video Streaming
Design a video streaming platform like YouTube or Netflix where users can upload videos, which are transcoded and served at scale to global audiences with adaptive bitrate streaming.
- Hard Complexity
- Interactive Canvas Playground
Design Web Crawler
Design a distributed web crawler like Googlebot that systematically discovers and downloads web pages at scale, for purposes like search indexing, archiving, or data mining.
- Intermediate Complexity
- Interactive Canvas Playground
Design Yelp
Design a local business discovery platform like Yelp or Google Maps where users can find nearby restaurants, services, and attractions; read/write reviews; and see ratings.
- Intermediate Complexity
- Interactive Canvas Playground
Design Stack Overflow
Explore the famous Stack Overflow architecture: a high-scale monolith done right with obsessive SQL tuning and aggressive caching, serving 56M users/month with only 9 web servers.
- Advanced Complexity
- Interactive Canvas Playground
