Stop passively studying. Start drawing architecture diagrams on an interactive whiteboard, recording your sessions, and comparing your solutions to expert answer keys — the closest thing to a mock system design interview you can do solo.
1 free beginner challenge — no credit card required
theonsite.dev gives you the tools to simulate a real system design whiteboard interview — pick a challenge, draw your architecture, and learn from expert solutions.
Draw architecture diagrams on an Excalidraw-powered infinite canvas — the same whiteboard experience you'll get in a real system design interview.
Practice under realistic time pressure with built-in timers matching real interview durations — 45 to 90 minutes depending on difficulty.
Record your entire practice session and replay it to spot gaps in your reasoning, improve your communication, and track progress over time.
After your attempt, reveal a detailed answer key written by engineers who've passed system design interviews at Google, Meta, Amazon, and more.
Curated questions that mirror what's actually asked in system design interviews at Google, Meta, Amazon, and top tech companies.
Build foundational skills with core infrastructure problems. Learn to discuss hashing, caching, database schemas, and CDN architecture.
and more...
Tackle the questions most commonly asked at top tech companies. Cover fan-out strategies, real-time messaging, distributed locking, and event-driven systems.
and more...
The hardest system design interview questions. Design video processing pipelines, geospatial matching engines, low-latency order books, and collaborative editing with CRDTs.
and more...
Built for engineers who want hands-on system design interview practice, not another video course
You're interviewing at Google, Meta, Amazon, Apple, Netflix, or Microsoft and need to nail the system design round to land the offer.
You're moving from mid-level to senior and need to demonstrate you can design systems at scale — not just build features.
You've built production systems but haven't practiced the interview format. You need a structured way to practice communicating your designs under time pressure.
Your first beginner challenge is completely free — no credit card required. Draw on the whiteboard, compare to the answer key, and see the difference active practice makes.