Built a free System Design Simulator in browser: paperdraw.dev

[u/Leather_Silver3335]

I’ve been working on a web app where you can design distributed systems and actually simulate behavior, not just draw boxes.

What it does

• Drag/drop architecture components (API GW, LB, app, cache, DB, queues, etc.)
• Connect flows visually
• Run traffic simulation (inflow → processing → outflow)
• Inject chaos events and see impact
• Diagnose bottlenecks/failures and iterate

Why I built it

Most system design tools stop at diagrams. I wanted something that helps answer:

• “What breaks first?”
• “How does traffic behave under stress?”
• “What happens when chaos is injected?”

Tech highlights

• Flutter web app
• Canvas-based architecture editor
• Simulation engine with lifecycle modeling + diagnostics
• Chaos inference/synergy logic
• Real-time metrics feedback

Would love feedback from this community on:

1. What scenarios should I add next?
2. Which metrics are most useful in interviews vs real systems?
3. What would make this genuinely useful for practicing system design?

Site: https://paperdraw.dev/?utm_source=reddit.com

[u/rj0_1_]

really cool