HI,
The plugin sends the notification to the topic.
The limitation is not the number of devices, but the number of messages sent to each device, as I understand
https://firebase.google.com/docs/cloud-messaging/concept-options
Maximum message rate to a single device
You can send up to 240 messages/minute and 5,000 messages/hour to a single device. This high threshold is meant to allow for short term bursts of traffic, such as when users are interacting rapidly over chat. This limit prevents errors in sending logic from inadvertently draining the battery on a device.
Upstream message limit
We limit upstream messages at 1,500,000/minute per project to avoid overloading upstream destination servers.
We limit upstream messages per device at 1,000/minute to protect against battery drain from bad app behavior.
Topic message limit
The topic subscription add/remove rate is limited to 3,000 QPS per project.
For message sending rates, see Fanout Throttling.
