FCM Scheduling API Development

I need a server-side script or API to send Firebase Cloud Messaging (FCM) notifications at specific or scheduled times. The react native expo at the moment is rescheduling only when app opens bit not in background or closed state.

Requirements:
- Notifications are alerts
- Handle sending FCM when app is in background and closed state ((terminated)

Ideal Skills and Experience:
- Proficient in React Native
- Skilled in Ubuntu server.
- Experience with Firebase Cloud Messaging
- Background in developing server-side scripts/APIs
- Familiarity with handling push notifications

Please include relevant experience in your application.