Free Simulator Teaches System Design by Letting You Watch Architectures Fail

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A developer has launched a free, browser-based interactive simulator designed to teach system design concepts through hands-on failure scenarios. Users begin with a single server and database handling 100 users, then watch performance degrade as traffic scales to 10 million, learning fixes like indexing, load balancing, caching, and circuit breakers along the way. The tool includes over 150 incident scenarios and 10 crisis simulations such as Black Friday surges, DDoS attacks, and cache stampedes. An Interview Lab feature presents real-world system breakdowns that mirror common technical interview questions, letting users diagnose and resolve issues themselves. Built as a proof of concept using vanilla HTML and JavaScript, the simulator is publicly accessible and the developer is seeking community feedback on future learning topics.

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