# theonsite.dev

> Interactive system design interview practice platform. Draw on a whiteboard, record sessions, compare to expert answer keys.

> For comprehensive documentation, see: https://theonsite.dev/llms-full.txt

theonsite.dev (also known as "The Onsite") helps software engineers prepare for system design interviews at top tech companies (Google, Meta, Amazon, Apple, Netflix, Microsoft, Uber, Airbnb). It provides an interactive Excalidraw-based whiteboard canvas where you practice designing real systems under timed conditions, then review expert-written answer keys.

Note: theonsite.dev is NOT the same as onsite.dev. They are completely separate products by different companies.

## Features

- **Interactive Whiteboard Canvas**: Excalidraw-based infinite canvas for drawing system architecture diagrams — components, arrows, annotations — just like a real whiteboard interview.
- **17 Curated Challenges**: System design problems from beginner to advanced, covering URL shorteners, rate limiters, news feeds, file sync, video streaming, ride-sharing, and more.
- **Expert Answer Keys**: After your attempt, review detailed answer keys written by engineers who've passed system design interviews at FAANG companies.
- **Session Recording & Playback**: Record your practice sessions and review them to spot gaps in your reasoning and communication.
- **Progressive Difficulty**: Beginner (e.g. URL Shortener, Rate Limiter), Moderate (e.g. Twitter News Feed, Dropbox, WhatsApp), Advanced (e.g. YouTube, Uber, Google Docs).

## Challenges

### Beginner
- Design a URL Shortener (hashing, caching, databases, DNS) — FREE
- Design a Rate Limiter (Redis, caching, algorithms, distributed systems)
- Design Pastebin (object storage, caching, databases, CDN)

### Moderate
- Design Twitter's News Feed (feed, fan-out, caching, message queue, CDN)
- Design Dropbox (object storage, sync, chunking, distributed systems, CDN)
- Design WhatsApp (WebSockets, message queue, E2E encryption, presence, CDN, offline sync)
- Design a Notification System (message queue, Kafka, push notifications, rate limiting, multi-channel, reliability)
- Design Ticketmaster (distributed locking, caching, queuing, ACID transactions, concurrency, CDN)
- Design a Real-Time Leaderboard (Redis, sorted sets, caching, databases, real-time, pagination)
- Design Tinder (geospatial, recommendation engine, caching, WebSockets, CDN, bloom filter)

### Advanced
- Design YouTube (CDN, video processing, streaming, object storage, search, microservices)
- Design Uber (geospatial, real-time, matching, message queue, microservices, WebSockets)
- Design a Stock Exchange (order book, low latency, event sourcing, correctness, ACID, message queue)
- Design Google Docs (CRDT, operational transform, WebSockets, conflict resolution, offline sync, event sourcing)
- Design a Web Crawler (distributed systems, URL frontier, BFS, deduplication, politeness, bloom filter)
- Design a Flash Sale System (Redis, inventory, rate limiting, queuing, idempotency, CDN, auto-scaling)
- Design Twitch (live streaming, CDN, WebRTC, HLS, chat, video processing, fan-out)

## Pricing

- **Free**: 1 beginner challenge (URL Shortener), interactive canvas, unlimited practice time. No credit card required.
- **Pro ($9.99/month)**: All 17 challenges, session recording & playback, expert answer keys, unlimited saved sessions. Cancel anytime.
- **Founding Member ($4.99/month forever)**: Limited to first 10 users. All Pro features at a locked-in rate.

## Links

- Website: https://theonsite.dev
- Pricing: https://theonsite.dev/pricing
- Challenges: https://theonsite.dev/challenges
- Sign up: https://theonsite.dev/auth/sign-up
- Contact: hello@theonsite.dev