Is it a good idea to use push notifications for mobile chat applications? (Android, iOS)

Question

The idea of using the push notifications is only to have a notification mechanism that will send a notification when there is a new message waiting to download from the backend service: all the notifications are of the same type e.g. "refresh messages from the server" (the same for Android and iOS).

Are there any limits for the Apple/Google push notifications services? Assuming that my application will handle more that 100k active users (or even 1M or more users) - would there be any problem with the Apple Push Notifications or GCM services?

If using the push notifications for such a service is not a good idea then what is other solution that could be used for mobile chat applications?

Answer 1

Don't forget that on iOS user may forbid sending notifications, so your app won't receive any even in foreground. Thus, you need to implement your own push mechanism.

Answer 2

Need for push notifications

Especially on iOS you don't have a choice but to use their push notifications service APNS. There is no other way to receive notifications immediately because iOS may kill or neglect the TCP connections of your background app.

On Android it seems possible to use your own background TCP connection to avoid having to use push notifications. But you may still consider the use of the push notifications through GCM for the sake of improved battery usage.

Pricing

Neither APNS (iOS) nor GCM (Android) charge you for the service and you are allowed to send an unlimited number of messages.

Limitations and Requirements

Both services will delete message, when there are too many messages accumulated in the queue for an offline device - which makes sense because there is no point in delivering those messages hours later. You have to take that in to account, when writing your app (just do a poll when going back online).

Depending on the app you are writing, there may also be privacy concerns. Even if you encrypt the message itself, at least Apple/Google know when a notification is sent to a certain device, which may be a deal-breaker for certain high-security applications.

You will also need a server that is able to communicate to both APNS and GCM. There are open source solutions for that (e.g. easyApns for iOS and python-gcm for Android), but how easy their integration is depends on your server and the language it is written in.