Hands-on system design

Build real systems.
Step by step.
In your browser.

Skip the tutorials. Implement Redis, rate limiters, and load balancers with tests that actually check your design choices.

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Free to start · Sign in to run · Runs in your browser

Real code, real tests

Every step compiles and runs in a sandbox. Your tests assert actual behavior, not "did you write the right function name".

You build it, guided

Every challenge breaks into 4 to 6 steps. You write the real code, and the instructions just keep you from getting stuck.

Ship-ready patterns

Strategy, WAL, event loops, token bucket. The structures you'll actually reach for at work.

Pricing
$20/month

 

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