"We’re writing to let you know that starting June 20, 2024 the legacy Firebase Cloud Messaging (FCM) APIs will be discontinued.

What do you need to know?

On June 20, 2024, we’re reducing the number of Firebase Cloud Messaging (FCM) legacy register APIs and legacy send APIs that provide similar functionality. This step will allow us to provide you with a more consistent experience and align with Google security standards to improve security, reliability and performance.

Because of these API decommissions, some already-deprecated SDKs and features will stop working after June 20, 2024.

Please consult the tables below to find which Firebase Cloud Messaging (FCM) APIs and corresponding services/SDKs/features will be discontinued and replaced with new alternatives.

This one is more relevant to me in the email

Discontinued Send API: Batch send API

Decommissioned service: Including multiple send requests in a single HTTP request to FCM known as Batch Send.

New alternative: Send messages via the HTTP v1 API, which has been optimized for fanout performance."

The deprecations are listed here:

https://firebase.google.com/support/faq#fcm-23-deprecation

I believe the topics solution they have isn't reliable for me as I have around 50,000 users on an application I work on and I send time sensitive notifications to them on a daily basis.

Is there an alternative to FCM that allows me to send to multiple devices at once almost instantly, perhaps like how WhatsApp or Twitter does their notifications?

Thanks.