Laravel offers conventions for building web applications, but maintainability still depends on choosing clear boundaries. The service container resolves dependencies; it does not decide where every business rule should live.
Trace the request lifecycle
A request passes through route matching and middleware before application behavior runs. Validate input at the boundary, authorize the requested action, apply a focused domain operation, and return a response that does not expose internal details.
Use dependency injection for real dependencies
Constructor or method injection makes dependencies visible and testable. Bind an interface when an implementation needs to change or be isolated, such as an external provider. Avoid creating a general-purpose service class for every small method without a cohesive responsibility.
Protect multi-step operations
Use policies for access decisions and transactions for related writes. Events and queues can separate follow-up work, but failures need a path to be observed. Operations that might be retried should be safe to repeat or protected by an idempotency strategy.
Review with tests
Feature tests can verify a complete request, persisted result, and authorization boundary. Unit tests can exercise isolated rules. Choose tests that explain the behavior and protect the next change.