What this is

1. What this is

A guide to system design interviews at twenty-four companies. The ones that pay the most and ask the hardest questions: Google, Stripe, Netflix, Meta, Apple, AWS, and the rest. We picked them because their loops are well-documented enough to dissect, and the bar at each is different in ways generic system design content papers over.

Every unit covers one real interview question at one company. Not "design Twitter" in the abstract. The actual phrasing someone got asked, broken down into what the interviewer was watching for, the two or three technical decisions you have to defend, and the things that get you a no-hire even when your diagram is fine.

If you've walked out of a system design round thinking "I drew the right diagram, why did they pass on me?" — you got scored on something you couldn't see. This course shows you what it was.

2. What's in here

Twenty-seven chapters.

The first one is foundation. The five things every panel scores you on. How to spend the thirty minutes you get. How to scope, estimate, draw, and defend choices. Read it once and you'll have the vocabulary that carries you through everything else.

Then twenty-four company chapters, one per company. Each one opens with how that company interviews: who's in the room, what the bar looks like at each level, what the cultural tells are. Then it walks through four to seven specific questions that company likes to ask. Google's distributed counter isn't Stripe's idempotency key, even though they look related. Confuse them and you get the wrong offer or no offer.

After the company chapters comes a chapter on the patterns that keep showing up across every loop. Rate limiting. Consistent hashing. Sagas. Distributed locking. Idempotency. CAP. Name them once and you'll recognize them everywhere.

The last chapter is the meta-game. Panels, signals, behavioral, the offer. By then the technical work is done. This chapter is the rest of the grade.

About a hundred and fifty units total. Big course. Worth it.

3. Who it's for

You, if you've:

• Walked out of a system design round and spent the train home replaying it.
• Been told you're "almost" senior with no specific feedback on what's missing.
• Read every public system design resource and noticed they're all the same six questions, none of which is the one you got.
• Had a take-home rejected with one line of feedback and no rubric.
• Watched a coworker with worse technical chops get the L6 offer because they talked about tradeoffs you also knew.

If you've never interviewed at this kind of company and don't plan to, this isn't the course for you. Read the free units to pick up the vocabulary and stop there.

4. What it isn't

Not a leetcode book. The coding round exists. We point at it once in the meta-game chapter. We don't teach binary search.

Not a behavioral framework. We touch the behavioral round once, in the chapter on how the bar raiser scores it, then move on.

Not a list of facts to memorize. The companies update their question banks every few months. What doesn't update is how the panel grades you. That's what's in here.

5. How each unit is shaped

Every onsite-scenario unit has the same ten parts, in this order:

1. The exact question, in the words someone got it.
2. What the interviewer was watching for.
3. What to ask in the first five minutes.
4. The arithmetic. Two minutes of numbers.
5. The diagram.
6. The two or three deep dives that decide the grade.
7. What breaks at ten times the scale.
8. The take-home version of the question, if there is one.
9. The green, yellow, red rubric. What gets you hired and what doesn't.
10. How a different company would grade the same answer.

Read enough of these and you start recognizing the shape of any new question the first time you see it. That's the thing you're paying for.

6. Next

The foundation chapter. Start with the five signals every panel scores you on. You'll come back to that page a lot.