Hey folks,

I’ve been hacking on a side project: a web-based “System Design Simulator.” It’s like a whiteboard, but you can actually press play and watch your architecture behave (or fail).

What you can do:

* Drag-and-drop common pieces: load balancer, API gateway, caches, DBs, queues, even some AI bits.
* Hit “Start Simulation” to see latency, error rate, throughput, cache hit rate in real time.
* Flip chaos switches: traffic spikes, cache-miss storms, network partitions, component crashes.
* Share & remix: every design gets a short link; anyone can fork it and improve.
* Built-in hints: it tells you if you forgot an entry point or storage.

Why I made it:

* Diagrams don’t fail; systems do. I wanted a fast way to feel trade-offs without spinning up infra.
* For interviews and design reviews, it’s nice to ask “what if the cache dies?” and just click a button.

Try it here: "[https://paperdraw.dev/](https://paperdraw.dev/)"

Quick start: drop Load Balancer → App Server → Cache → DB, press play, then trigger a cache-miss storm.

Would love feedback:

* What metrics or failure modes would you add?
* Is the start/stop flow obvious enough?
* Any presets you want (payments, chat, ingestion)?
* Should I add “export GIF of the run” for sharing?

Thanks for taking a look—happy to fix bugs or add features if you ping me.

[](/submit/?source_id=t3_1recj56)



I built a System Design Simulator – drag, simulate, and break your own architectures in minutes