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

Pratap Vhatkar — Tue, 10 Mar 2026 09:06:37 +0000

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/"

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.

DEV Community: Pratap Vhatkar

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