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Interview prep.

The course teaches it; this gets you hired. See what each company asks, work the classic problems, sit a timed mock (alone or with a real person), and revise the night before.

lessons revised: –/75
labs cleared: –/16
mocks done: –/8
study plan: …

how each tool works →

video lecturesWatch it, in order

Every lecture in course sequence, then the side quests and the rest.

all lectures184 lectures

The whole playlist

Animated, narrated lectures for the course's lessons, the side quests and more: the idea, where the obvious design breaks, the real one, and what to say. Quiz checkpoints, and ask the AI about any moment.

jump to

55 h 14 min · captions · chapters

start herelecture 1

System design fundamentals: where do you even start?

Begin at the first lecture and keep going: each one ends by playing the next, and picks up where you left off.

in course order · resumes where you stopped

design canvasDraw it, get it reviewed

The whiteboard round, on your own time: any interview problem, any capstone, or your own system.

whiteboard + ai reviewnew

Design canvas

Sketch the architecture with blocks, tech logos and arrows, then get a staff-engineer review of what you drew: the gaps worst first, the fix for each, and what you'd be asked next. Saves to your account.

interview problems · capstones · your own idea

mock interviewsSit a real interview loop

A timed round with an interviewer, curveballs, a rubric and a verdict. Watch the recorded one first if you like.

M1 · after world 01PaislyPhone OTP sign-in and sessions

45 min · 6 phases · 3 curveballs · with Nandini Hegde

Start the round Watch it done well · 47 min

M2 · after world 02BillboltBill payments and AutoPay

45 min · 7 phases · 3 curveballs · with Ananya Rao

Start the round Watch it done well · 48 min

M3 · after world 04CartwalaFlash-sale catalog and prices

50 min · 7 phases · 3 curveballs · with Revathi Menon

Start the round Watch it done well · 47 min

M4 · after world 05WanderstayStays booking and availability

50 min · 7 phases · 3 curveballs · with Marco Lindqvist

Start the round Watch it done well · 52 min

M5 · after world 07SunwaaiSupport desk, ticket search and SLAs

50 min · 7 phases · 3 curveballs · with Farhan Qureshi

Start the round Watch it done well · 48 min

M6 · after world 08KaamkaajJob search, alerts and recruiter analytics

50 min · 7 phases · 3 curveballs · with Kabir Sethi

Start the round Watch it done well · 52 min

M7 · after world 09SwitchyardMulti-tenant feature flags and experiments

50 min · 7 phases · 3 curveballs · with Zoya Kapadia

Start the round Watch it done well · 48 min

M8 · after world 10TillsyOffline-first POS platform (final loop)

60 min · 7 phases · 3 curveballs · with Dr. Meera Iyer

Start the round Watch it done well · 48 min

who's hiringPrep for a company

What candidates reported, with sources, and the lessons that teach it.

showing 12 of 45 · search above or see them all

All 45 companies Question bank · 353 questions · 292 reported

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.

classic problemsThe questions everyone asks

Short walkthroughs that link into the full lessons.

Low-level design

Machine coding: classes, interfaces, patterns

interview nightRevise fast

For the evening before, or the train to the office.

revision decks

Five minutes a lesson

Swipeable cards: key ideas, numbers to remember, the trade-off table, classic mistakes and what to say when asked.

revise a world

696 cards · 75 lessons

cheat sheets12 worlds

A whole world on one page

Prints on a single A4 or Letter sheet. Download it as a PDF or share the link.

open a sheet

print · PDF · share

design sheets36 side quests

A whole design in ten minutes

Each side quest on a few pages: the numbers, the architecture with real tech icons, sequence, class and state diagrams, the decisions and what breaks.

open a sheet

245 diagrams · PDF · share

the real loopDo it for real

Timed rounds, a real person, working code.

code labs

Implement it in Python

A rate limiter, an LRU cache, a hash ring, an outbox relay: write it in the browser and run it against hidden tests.

runs on your device

mock interviews

The real loop, timed

An unseen problem from a fictional company, a named interviewer, curveballs, then a levelled rubric and a verdict.

8 loops between worlds

peer mockswith a real person

Practise with another learner

Post a time and a mock, someone pairs up, you both get a free video room. One interviews, then you swap.

needs an account

war roomsyou're on call

Take the page

A SEV-1 plays out in the incident channel and you make the calls. Each night is modelled on a real postmortem: practice for on-call and for “tell me about an incident”.

29 incident nights · 8–15 min

toolsNumbers and a plan

Estimate out loud; plan to your interview date.

numbers playgroundworks offline

50k QPS × 2 KB × 30 days = ?

Type an estimate the way you'd say it and get the worked answer, next to the latency and size numbers the course teaches.

calculator · reference numbers

study planner

Plan to your interview date

A day-by-day plan from your real progress, with revision days at the end. Fall behind and it adjusts.

calendar file · Google Calendar

video lecturesWatch it, in order

design canvasDraw it, get it reviewed

mock interviewsSit a real interview loop

who's hiringPrep for a company

classic problemsThe questions everyone asks

Problem bank

Low-level design

interview nightRevise fast

the real loopDo it for real

toolsNumbers and a plan