Three short lessons.
Built to be read once and remembered forever.
No fluff, no nine-tab spreadsheets, no twenty-minute YouTube intros. Open a card. Learn the thing. Close the tab smarter.
Lesson 01 · Networking
How DNS actually resolves a URL
From the browser to the authoritative server in five hops. With the CNAME chain explained for once.
Lesson 02 · Algorithms
The Big-O cheat sheet that finally clicks
Eight complexity classes. One mental model. Real-world operations mapped to each curve.
Lesson 03 · Systems
Anatomy of a modern web app
DNS → CDN → app server → database. Every layer, what it does, and where things go wrong.