Is system In Pain

Learn system design the painful way — the way that sticks. Build real systems, run traffic through them, and watch them break.

Deterministic simulator — same architecture, same result, every time. No signup.

↘ flip the scenario

SIM · TINYURL-1PASSING

traffic

100 req/min

p99

142ms

avail

99.9%

score

DATABASE OVERLOADCACHE MISS STORMQUEUE BACKLOGAPI TIMEOUTRATE LIMIT REACHEDREGIONAL OUTAGESERVER CRASHNETWORK LATENCY SPIKEREPLICATION LAGCONNECTION POOL EXHAUSTEDDATABASE OVERLOADCACHE MISS STORMQUEUE BACKLOGAPI TIMEOUTRATE LIMIT REACHEDREGIONAL OUTAGESERVER CRASHNETWORK LATENCY SPIKEREPLICATION LAGCONNECTION POOL EXHAUSTED

Learning through cause & effect.

THE LOOP →

Build

Drag components onto the canvas and wire a real architecture.

Simulate

Run live traffic through a deterministic engine — packets and all.

Observe

Watch nodes saturate, queues back up, bottlenecks turn red.

Optimize

Scored on latency, cost, resilience. Never on checkboxes.

One server → planet scale.

Foundations

URL Shortener · Blog · Todo

Scaling

Chat · Food Delivery · E-commerce

Distributed

WhatsApp · Instagram · Netflix

Enterprise

YouTube · Uber · Amazon

Break your first system.

Five levels. A deterministic engine. Zero diagrams to memorize.

systemInPain.com — the Duolingo of system design