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systemInPain

Launching today

Learn system design by watching it break in real time

2 followers

Learn system design by watching it break in real time

2 followers

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Build an architecture, then throw real simulated traffic at it. systemInPain runs a deterministic queueing-and-network simulator underneath — no keyword scoring. Watch p99 spike, nodes saturate red, and queues back up live. 15 levels, free to start,

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Launch tags:Design Tools•Education•Developer Tools

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Hey Product Hunt 👋 Most "system design practice" is either a whiteboard with no feedback, or a quiz that scores you for having the right buzzwords in the right boxes. I wanted something that actually tells you when you're wrong — the way a real system does, under real load. systemInPain is a system design game where you drag components (load balancers, caches, queues, replicas...) onto a canvas, wire them into an architecture, and hit simulate. A deterministic engine runs seeded traffic through your graph and measures what actually happens: p99 latency, availability, cost per hour, throughput. Get the fan-out wrong and load doubles instead of halves. Skip the cache and watch your DB melt. Forget a queue and bursts drop requests. It's graded, not guessed. 15 levels take you from a basic TinyURL clone through flash-sale traffic spikes, read replicas, CDNs, async write queues, failover, and bot/DDoS traffic — each one teaching a single, specific lesson you can see land or fail. Level 1 is free, no signup. It's still early — would love your feedback (there's a link right in the footer, it comes straight to me). Try it: systeminpain.com

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3d ago

honestly this looks great for actually seeing where things break. one thing that would help me a lot though is letting you replay a level and tweak just one variable like node count or arrival rate, basically see how small changes shift p99 without redoing everything from scratch

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14h ago

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3d ago

Why I built a real simulator instead of another system design quiz

Most system design "practice" grades you on whether you drew the right boxes cache here, load balancer there checked against a keyword list. That never sat right with me, because the actual skill being tested in a system design interview isn't "do you know the vocabulary?" it's "Can you reason about what happens to this system under load."

So SystemInPain doesn't grade the diagram. It runs it. There's a deterministic simulation engine underneath the same architecture and the same seed always produce the exact same result and it pushes real seeded traffic through whatever you build, then measures p99 latency, availability, cost, and throughput under both steady load and injected failure scenarios (traffic spikes, node outages, and bot floods).

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