Model observers vs event listeners in Laravel: when to use which
Both model observers and event listeners can respond to Eloquent events. In practice, when do you use one over the other?
Observers are good for side effects that are tightly coupled to a specific model: caching invalidation, audit logging, denormalized counter updates. They are registered in the model or service provider and are easy to find.
Event listeners are better when the reaction is decoupled from the model: sending emails, triggering jobs, updating external systems. The model fires an event, multiple listeners can react independently without the model knowing about them.
The testability difference matters: observers are harder to isolate in unit tests because they fire automatically. Event listeners can be faked with Event::fake() cleanly.
Observers can silently cause performance issues because they fire on every create/update/delete including during bulk operations like seeders or data migrations. Use Model::withoutObservers() or Observer::disableAll() in such contexts.
We moved from observers to model events dispatched explicitly in service methods. More verbose but the execution flow is obvious when reading the service code. Implicit observer firing made it hard to understand what happens on a save.
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