Google Cloud Messaging: State of the Union

Google Cloud Messaging (GCM) is a robust infrastructure used for distributing messages across multiple devices, including Android, iOS, and web browsers, delivering over 150 billion messages daily. GCM offers various techniques for message delivery, such as targeting single devices with unique registration tokens, grouping multiple devices for unified notifications, and creating subscription-based topics for interest groups without limitations on subscriber numbers. Despite potential connectivity issues influenced by carriers and local settings, GCM maintains a high delivery speed, with 95% of notifications reaching devices within 250 milliseconds. Google continues to enhance GCM, adding features like an API for migrating iOS notification infrastructures to GCM without altering client code, and the InstanceID API for seamless subscription to topics, enabling efficient notification dissemination. Resources are available for developers to build applications using GCM, including a 'GCM Playground' on GitHub and comprehensive guides for Android and iOS development, with promises of ongoing innovations in the platform.