Passive study doesn't prepare you for a 45-minute whiteboard session. theonsite.dev is a hands-on system design interview preparation platform where you practice drawing architectures, recording your sessions, and comparing to expert answer keys.
1 free beginner challenge — no credit card required
Most engineers prepare for system design interviews by consuming content. But the interview isn't a quiz — it's a live design session. And consuming content doesn't prepare you to perform.
You understand the theory but freeze when you have to actually draw a system from scratch on a blank whiteboard.
You can recall individual concepts but struggle to structure a coherent 45-minute design session end to end.
You know the buzzwords — fan-out, sharding, CRDT — but can't explain when to use each one under interview pressure.
Active practice is the fastest path to system design interview readiness. This is the loop that theonsite.dev is built around.
Choose from 17 curated system design questions organized by difficulty — beginner, moderate, or advanced. Each matches real questions asked at top companies.
Open the interactive Excalidraw canvas and design your architecture under timed conditions. Draw components, databases, queues, load balancers — everything you'd sketch in a real interview.
Hit record and practice explaining your design out loud as you draw. Replay the recording to hear how you communicate trade-offs and identify gaps in your reasoning.
Reveal a detailed expert answer key written by engineers who've passed these interviews at Google, Meta, and Amazon. See what you missed and learn better approaches.
A complete system design interview prep toolkit — not another video course or flashcard app.
Excalidraw-powered infinite canvas for drawing architecture diagrams — the same experience as a real whiteboard interview.
Record and replay your practice sessions to review your thought process, communication, and time management.
Detailed reference solutions for every challenge, written by engineers at top tech companies.
17 challenges across three levels — start with beginner and work up to the hardest problems asked at FAANG.
Each challenge has a time limit matching real interview constraints — 45 to 90 minutes depending on complexity.
Attempt each challenge as many times as you want. Track your improvement across sessions.
Our challenges cover the same system design topics asked at these companies and many more. Whether you're targeting FAANG or a high-growth startup, the fundamentals are the same.
Start free, upgrade when you're ready
$8.25/mo · $19/mo
Your first challenge is free. Open the whiteboard, draw your architecture, and see why active practice is the fastest way to get system design interview ready.
Start for free