OneSignal is our current solution for dispatching push notifications to our React Native App via our backend.

One of our use cases is to target users with payments due soon by send them a notification with the amount. We might have hundreds of thousands of users we need to dispatch to at once – each with their own amounts of course. The problem is that there doesn’t seem to be a way to dispatch personalized notifications with custom data in batches, rather we’re going to have to do it request at a time. We can parallelize this but we can only have so many threads

OneSignal has a rate limit of 6000 requests per second per app, but is this enough/scalable?

Sending personalized push notifications using onesignal – this seems to still be the case