The shape of the whole application

someone said three-tier and meant three folders, and someone else heard three machines.

Tier vs layer

the browser posted to a controller, which changed the model and picked a view, and the view read the model itself.

Model-view-controller

every request in the application arrives at one handler first, and that is where authentication and routing live.

Front controller

the view is an interface with setTitle and showError on it, and the presenter is what you actually unit test.

Model-view-presenter

the class that touches the framework has no logic in it, so the logic is testable without the framework.

Humble object

there is an object holding the state of the screen — what is selected, what is disabled — and it is not the domain object.

Presentation model

you changed a property on the viewmodel and the label updated, and no code you wrote connected the two.

Model-view-viewmodel

typing in the box changed the object and changing the object changed the box, and tracing which caused which was work.

Two-way data binding

the same use case runs from an HTTP handler, a message consumer and a test, and none of them is the primary one.

Hexagonal architecture

an import from the domain package to the database package failed the build, and the arrow only ever points inward.

Dependency rule

the domain model sits in the middle with no dependencies at all, and everything else wraps around it.

Onion architecture

entities, then use cases, then adapters, then frameworks — and nothing in an inner circle names anything outside it.

Clean architecture

there is one class per thing a user can do, with one public method, and its name is a verb.

Use case interactor

one change touched one folder, instead of the same change touching the controllers, services and repositories folders.

Package by feature

you opened the top-level folder and learned what the system does, rather than which framework it was written in.

Screaming architecture

someone added a feature by dropping in a package, and you did not change or redeploy the application to allow it.

Plugin architecture

the product is a small core that does almost nothing, and every feature anyone names is a plugin.

Microkernel architecture

each stage takes one thing and returns another, knows nothing about its neighbours, and you reordered two of them safely.

Pipes and filters

several independent components read from and write to one shared workspace, and no one of them owns the answer.

Blackboard pattern