Hands-on system design

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

Skip the tutorials. Build 59 real systems, from Redis and rate limiters to Raft, with tests that check your design choices.

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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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  • All 59 real-systems challenges
  • Fundamentals free, no card needed
  • Browser IDE with real test execution
  • New system every newsletter issue