A Firebase Cloud Messaging (FCM) developer is responsible for integrating and utilizing Google's Firebase Cloud Messaging service into applications. This involves setting up SDKs, creating and managing messaging campaigns, handling notifications, and troubleshooting issues. FCM developers ensure reliable and efficient delivery of messages or notifications from servers to devices, enhancing real-time engagement and interaction. They also manage topics and subscriptions, and implement data messages for background updates. The role requires a sound understanding of Firebase, cloud technology, and mobile app development. They play a crucial role in enhancing user experience by facilitating real-time communication and updates.