How to play.
Practice the system design questions common in modern technical interviews.
Full answer · about ten minutes
Read a scenario, then write your decisions across five rounds: requirements, architecture, a hard detail, a failure, and a trade-off. You can use one hint per round. Submit all five to see feedback and model answers. Daily completion builds your Full streak; past puzzles are available in the archive.
Quick · two to three minutes
Read a different daily scenario and choose the best answer to three multiple choice questions. The options test your system design judgment and trade-offs. Once you submit all three, you can review the correct choices and explanations. Quick has its own streak and progress; you can play both modes on the same day.
New daily content follows your profile's time zone. Your choices in Quick do not change the Full leaderboard.
Start practicing