Are push notifications reliable?

Question

Mobile development

Friends, please help me figure it out.
By my order, a taxi call application for Android and iOS is being developed.
Do I understand correctly that push notifications will allow taxi drivers to know about incoming orders even when the application is turned off, and this is the only reasonable way to signal an order when the application is closed?
However, the developers dissuade me in every possible way from using the push functionality.
Here, they write:
1. They are not reliable! There is no guarantee that push notifications will be delivered even if APNS accepts them.
Once your server has generated a push notification, it silently sends it to APNS. There is no way to know the delivery status of a notification to an end user after it has been sent. Delivery time can vary from a few seconds to half an hour.
2. They can be expensive! Adding push functionality to an app is pretty easy and inexpensive if you own the data. However, if you have many users or need to query for data, then the cost increases dramatically.
Tell me, please, are they right? And why the same viber or skype pushes function normally. Maybe our developers are doing something wrong?
Thanks in advance for the detailed answers.

Answer 1

1. There really is no guarantee. But if the application is closed, then it's better than nothing.
2. The subscriber token is used there (a string, I don’t remember how many characters). This application token, after updating and authorization, after asking for permission, gives it to your host and to the apple host to subscribe to events. It is not clear what kind of data is supposed to be requested, it is worth clarifying with them.

Answer 2

Roman is right, there really is no guarantee of real-time delivery. For example, a simple case: at the time of delivery of the notification, the user was offline. In this case, GCM will delay the delivery for several hours.
As for the price of push notifications, nothing is clear - what do you have to pay for? Sending notifications is free, registering a device in APNS is also free. Or do you use some third-party service to send push notifications?

Answer 3

Make your push service, and on the android device start the receiving service as startForeground. And of course lower the connection timeout.

Answer 4

Ready to help launch your own push notification mailing server. I can also help with iOS.