- NestJS – Providers and Dependency Injection
How Nest builds your object graph. @Injectable, constructor injection and what the emitted metadata is actually doing, provider tokens beyond the class — useValue, useFactory and useClass, why an async factory is the only way to configure a module from config, injection scopes and the reason singletons are the right default.
- Java 11 Removed/Deprecated Features & Migration
Java 11 is the upgrade that breaks things. Not because the language changed — it barely did — but because Java 11 removed several modules that had been part of the JDK since the 1990s. Most upgrades from 8 fail for the same handful of reasons, and they are all fixable. Why this one hurts Java 9…
- Hash Tables
Turn the key into an array index and go straight there. Separate chaining, the load factor, why resizing has to rehash rather than copy, what a bad hashCode does to your O(1), and the equals/hashCode contract that breaks lookups when you get it wrong.
- Angular – RxJS, and How Much of It You Still Need
Signals took over state, but observables still own events over time. Built around one worked example — the menu search box — where `toObservable`, `debounceTime`, `distinctUntilChanged`, `switchMap` and `catchError` each fix a specific bug, and `toSignal` hands the result back to the template. Why `switchMap` and not `mergeMap` is the difference between correct and subtly wrong.
- Docker – Logs, Exec and Debugging a Container
Your container exited, or it says `unhealthy`, or it will not connect to the database. `logs -f`, `exec -it sh` into a running container, `inspect` for the config it actually got, `stats` for resources, what the exit code means, and the healthcheck that reported unhealthy forever because the image had no `curl` in it.