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System Design Mastery.

A 12-world campaign for backend engineers going from intermediate to advanced. Clear a world's lessons, beat its interview boss, pass the trial, and move on to the next. After most worlds, a timed mock interview loop checks it all under real interview pressure. Nothing is locked.

12worlds

75core lessons

11bosses

36side quests

8mock interviews

~144hof reading

how the course works: stages, XP, trials, Arena →read the guide →

Skill tree

donecurrentaheadbosstrial partmock interview

P1P2P3P4P5P6P7P8T1T2T3T4T5T6T7T8
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MOCK 01 · INTERVIEW LOOPPaislyPhone OTP sign-in and sessions45 min · 6 phases · 3 curveballs · covers W00–W01 · with Nandini HegdeAHEAD
PRED1D2D3D4D5BT1T2T3T4T5T6
MOCK 02 · INTERVIEW LOOPBillboltBill payments and AutoPay45 min · 7 phases · 3 curveballs · covers W00–W02 · with Ananya RaoAHEAD
PRED1D2D3D4D5BT1T2T3T4T5T6
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MOCK 03 · INTERVIEW LOOPCartwalaFlash-sale catalog and prices50 min · 7 phases · 3 curveballs · covers W00–W04 · with Revathi MenonAHEAD
PRED1D2D3D4D5BT1T2T3T4T5T6
MOCK 04 · INTERVIEW LOOPWanderstayStays booking and availability50 min · 7 phases · 3 curveballs · covers W00–W05 · with Marco LindqvistAHEAD
PRED1D2D3D4D5BT1T2T3T4T5T6
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MOCK 05 · INTERVIEW LOOPSunwaaiSupport desk, ticket search and SLAs50 min · 7 phases · 3 curveballs · covers W00–W07 · with Farhan QureshiAHEAD
PRED1D2D3D4D5D6BT1T2T3T4T5T6T7
MOCK 06 · INTERVIEW LOOPKaamkaajJob search, alerts and recruiter analytics50 min · 7 phases · 3 curveballs · covers W00–W08 · with Kabir SethiAHEAD
PRED1D2D3D4D5BT1T2T3T4T5T6
MOCK 07 · INTERVIEW LOOPSwitchyardMulti-tenant feature flags and experiments50 min · 7 phases · 3 curveballs · covers W00–W09 · with Zoya KapadiaAHEAD
PRED1D2D3D4D5BT1T2T3T4T5T6
MOCK 08 · INTERVIEW LOOPTillsyOffline-first POS platform (final loop)60 min · 7 phases · 3 curveballs · covers W00–W10 · with Dr. Meera IyerAHEAD
PRED1D2D3D4D5BT1T2T3T4T5T6

Shorts

556 ideas in under two minutes each, swipe through them like Reels. watch all ›

Side quests

Real systems, designed end to end, easiest first. All open. +120 XP each. design sheets →Company names and logos are trademarks of their owners, shown only to identify each company. This course isn't affiliated with or endorsed by any of them.

Beyond the course

prep · get hiredInterview prep →Company pages with what candidates were asked, the question bank, 20 classic problems, 22 low-level design rounds, timed mocks, cheat and design sheets.arena · playArena →The daily challenge, weekly leagues, quick games, your review queue and design of the week.stories · see it for realWar stories →True stories of real systems at their limits, and war rooms where you take the page.

in the course too:concepts A–Z →reading trail →side-quest design sheets →

No internet? No problem

Read offline

Save a lesson, a world or the whole course and read it on a flight. Diagrams, code, quick checks and trials work with no connection, and your progress syncs when you land.

Offline library