- Big O Notation
How an algorithm's cost grows as the input grows — the only performance question that survives a change of hardware. The common classes from O(1) to O(2^n), how to read a complexity off a loop, why constants are dropped, and the difference between time and space complexity.
- React Native – Animations and the Native Driver
The `Animated` API, and the one flag that matters: `useNativeDriver`. With it the animation runs on the UI thread and stays smooth while JavaScript is busy; without it every frame crosses the bridge. Which properties can be driven natively and which cannot, `interpolate`, starting an animation in an effect rather than in render, and where Reanimated takes over.
- Spring Boot – API Docs with springdoc-openapi
Springfox is dead; springdoc is what generates OpenAPI 3 from your controllers now. Wiring it up, documenting an endpoint properly, describing JWT auth so the Try It Out button works — and the version pin Boot 4 forces on you, because Boot no longer manages springdoc's version.
- TypeScript – Get Started
Start here. What TypeScript actually is — a type checker that erases itself, not a language that runs — the three kinds of bug it catches and the one class it cannot, the exact versions this track is written against, the pizza ordering app every example is taken from, and the full lesson index in reading order.
- Python – String Methods
The string methods worth memorising — strip, split, join, replace, startswith, and the case pair — plus slicing, why strings are immutable, and why building one in a loop with `+=` is the wrong tool.