Modules and providers.
WHAT A MODULE IS
A grouping of related controllers and providers, with declared imports and exports.
WHY MODULES MATTER
They define what is available where, which prevents accidental coupling.
WHAT A PROVIDER IS
Anything injectable: services, repositories, factories.
WHAT TO EXPORT
Only what other modules genuinely need.
WHY
Exporting everything defeats the boundary.
WHAT TO PUT IN A CONTROLLER
Request handling, validation binding, and response shaping.
WHAT TO PUT IN A SERVICE
Business logic.
WHAT TO AVOID
Services depending on controllers Circular imports between modules A single module containing everything
WHAT PIPES PROVIDE
Transformation and validation of incoming data.
WHAT GUARDS PROVIDE
Authorisation decisions, before a handler runs.
WHAT INTERCEPTORS PROVIDE
Behaviour around handlers: logging, transformation, caching.
WHAT TO USE THEM FOR
Cross-cutting concerns, rather than repeating logic in every handler.
WHAT TO CONFIGURE GLOBALLY
Validation, so every endpoint validates by default.
WHY
Opt-in validation is eventually forgotten somewhere.
