- Spring Boot

- Android (Jetpack Compose)

- Kotlin

I want my Spring Boot backend to send FCM notifications when an order status changes.

Before writing code, I'd like to understand the recommended project structure.

For example:

- Where should Firebase initialization be placed?

- Should I create a dedicated NotificationService?

- Where should the service account JSON be stored?

- How should the FirebaseMessaging instance be configured?

I'm not asking how to send a notification itself—I want to understand the recommended architecture for integrating FCM into a Spring Boot project.