Open beta · Free
The practice-first way to learn system design. Step-by-step lessons, graded quizzes, and an interactive design lab where you build architectures yourself.
01 — Demo
Pick a challenge, place the components, run a load test, and get a reviewer's verdict. No signup — this is how learning here feels.
Step 1 of 4
Pick a challenge
60 seconds · No signup
Activity
Welcome to the design lab. Pick a challenge to begin.
No rush — mastery is a loop.
02 — Traffic lab
Pick a scenario and watch latency, queues, and hit rates respond. Every challenge runs its own behavioral model — nothing here is random.
Read-heavy and cacheable. The classic first design.
Healthyall systems nominalPick a scenario
Client
Load Balancer
App
Cache
Database
Timing waterfall
p50 latency
2.8ms
p99 latency
6.2ms
throughput
925rps
timeouts
0%
queue depth
0
messages waiting
cache hit rate
95%
higher is better
replica lag
8.8ms
staleness window
10.8ms
how stale reads can be
What a reviewer would notice
03 — How it works
One idea per lesson, then immediate practice. The loop is the curriculum.
01
Focused lessons with architecture diagrams. Understand why each component exists before you memorize anything.
02
Scenario questions graded instantly, with explanations for every answer. Weak spots get flagged automatically.
03
Open the design lab, pick a challenge — URL shortener, rate limiter, chat — and build the architecture hands-on.
04 — Free beta
Everything is open while we're in beta. Learn first — that's the whole point right now.
Beta access
Free
No credit card · No catch
Your progress stays yours.
FAQ
Engineers who want real depth in system design — from first principles to principal-level judgment. If you'd rather build than memorize, you'll fit right in.
Reading is passive. Every concept here ends with doing: quizzes that grade your reasoning, and a lab where you place components and watch them behave under load.
Yes — everything is free during the open beta: all lessons, quizzes, and the design lab. No credit card, no catch.
We'll say so well in advance. Your progress and everything you've completed stay yours.