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89 concepts across 8 areas, connected by what you have to know first. Every explanation ends in a question you answer from memory.

89 written so far.

Web & Networking

How a request actually crosses the internet, and the protocol everything else is built on.

14 concepts · 8 hours

Frontend Engineering

The browser platform, the language, and the frameworks that render state to a screen.

28 concepts · 19 hours

Backend Engineering

Servers that answer correctly under load, under retry, and under attack.

15 concepts · 10 hours

Data & Storage

Where state lives, how it stays correct, and why the query got slow.

14 concepts · 10 hours

Systems & Scale

What breaks when one machine becomes many, and when two things happen at once.

12 concepts · 8 hours

Infrastructure & Delivery

Getting code to production repeatably, and knowing what it did when it got there.

7 concepts · 4 hours

Engineering Craft

The habits that separate someone who writes code from someone you want on the team.

9 concepts · 5 hours

Computer Science

The vocabulary every technical interview assumes you already have.

3 concepts · 3 hours