Your app
Messenger
Viber
Telegram
Slack
SMS
Apple APNs "best effort" push service
See APNs docs
APNs does not guarantee the delivery of your push notifications. For example during multiple message sending if the smartphone is switched off only the last message will be delivered while all the others will be discarded.
Android FCM / HMS "best effort" push service
See FCM docs
If your application is closed by the user in settings, the push notification will be received by the smartphone but it will be discarded and it will not be accessible by the mobile user.
Competitors' "best effort" push services
Parse, Urban Airship, Pushwoosh and other main push providers use Apple APNs and Android FCM / HMS best effort push services as content delivery channel thus they cannot neither guarantee the delivery of your push messages nor provide a real time delivery status tracking.
Go beyond APNs and FCM “best effort” push delivery if notifications are an important part of your real time app!
See competitors' benchmarking
