- NestJS – Guards
CanActivate, and the one question a guard answers: may this request proceed? A real JWT guard in about thirty lines, why verifyAsync and never decode, why guard order in @UseGuards is load-bearing, and where a guard stops being the right tool — the check that needs to read the row belongs in the service.
- Python – OOP
Inheritance, composition and polymorphism in a language with duck typing, where an interface is a set of methods rather than a declaration. `super()`, properties, abstract base classes, and when to prefer composition.
- Java 21 Pattern Matching for switch
Java 21 lets a switch match on types, not just constants. Combined with sealed types , it turns a chain of instanceof checks into something the compiler can prove is complete. The chain it replaces Each case tests a type and binds a variable of that type, the same as instanceof pattern matching .…
- Angular – Template-Driven Forms
The quicker of Angular's two form systems, and the right choice for a short form. `FormsModule` and `ngModel`, `ngForm` and template reference variables, the built-in validators, showing an error only once the field has been touched, and the point at which you should stop and reach for reactive forms instead.
- Docker Compose – Profiles, Overrides and Multiple Files
Not every service should start every time. Compose profiles put Elasticsearch, a message broker and a mail sink behind opt-in flags so the default `up` starts one container. Then `compose.override.yaml`, stacking `-f` files for dev and prod, and how `${VAR}` and `.env` interpolation works.