- What a Data Structure Actually Is
A data structure is a decision about how to lay data out in memory, and an algorithm is a decision about how to walk it. Why there is no best structure, the four questions that pick one, and the Java collection each choice maps onto.
- React – State with useState
State is what a component remembers between renders. Why a plain variable will not do, the array destructuring useState returns, the rules that govern where hooks may be called, one state variable versus several, and the moment to stop and lift state up to a shared parent instead.
- Angular – Signals
Signals are how Angular tracks state now, and they are the biggest change to the framework in years. What a signal is, `signal()`, `set()` and `update()`, why reading one inside a template subscribes that template to it, and how signals let Angular skip change detection for everything that did not change.
- Docker – Multi-Stage Builds
Build in one image, ship from another. The pizza API compiles with Maven and a full JDK, then copies one jar into a JRE image — no Maven, no source, no build cache in the result. The frontends do the same with Node and nginx. Named stages, `COPY --from`, and stopping at a stage with `--target`.
- Hasura – Queries
The query language you get for free. `where` with `_eq`, `_gt`, `_in`, `_like`, `_and`/`_or`/`_not`, then `order_by`, `limit`/`offset`, cursor pagination, aggregates and `distinct_on` — each shown with the real response from a running engine. Also the naming-convention setting that decides whether your fields come back `price_per_night` or `pricePerNight`, and what it looks like in v3.