Normally push notifications do arrive quite quickly. The most common reason for notifications being delayed is the device had no internet connection or a poor connection and the notification did not arrive until the connection was made.
When notifications get sent from from Kura via our push notification provider, they go to Google (FCM), Apple (APNS), Windows (WNS), and other messaging servers. Our provider is in charge of sending these requests to these Push Servers which then deliver it to your subscribers.
Push notifications are typically sent to the Google or Apple servers in 0.5 seconds.
If the device receiving the push does not get it right away, it could be an issue with the FCM, APNS servers (rare) or the device had unstable internet causing a delay (common).
Other issues can be as follows:
Delays for notifications on Android Devices:
Some home and commercial wifi routers will cause the device's connection to Google's FCM servers to be closed. The device later re-opens the connection and receives the delayed notifications. (Discussed here: https://groups.google.com/forum/#!topic/android-gcm/Y33c9ib54jY)
Some custom versions of the Android OS have a "power-saving" setting that can cause notifications to be delayed or ignored. For instance, Sony Xperia devices have a "Stamina Mode" and other device's have similar modes discussed in our Notification Not Shown Guide
Some Android devices can enter a low power mode when their battery is low that may cause slight delays in receiving notifications. This is more common on Android 9 devices with the New Power Management Restrictions:
- Notification Priority can delay notifications depending on the device's battery level and settings.
Delays for notifications on iOS devices:
As with Android, some wifi routers will cause iOS notification delivery delays.
Notifications may be delayed if "Restrict background data" is checked for the app, if Wifi-Optimization is turned on in the advanced settings, or if priority mode is enabled.
"Low Power Mode" is enabled. If in your Settings > Battery > Low Power Mode is enabled, this will reduce the rate at which notifications can be received or turn them off completely.
WhatsApp has a good list of instructions on troubleshooting delayed Android and iOS notification at the bottom of their FAQ page here: https://www.whatsapp.com/faq/en/android/20887936
Delays for notifications on Web:
As with Android, some home and commercial wifi routers will cause the device's connection to Google's FCM/GCM servers to be closed. The device later re-opens the connection and receives the delayed notifications. (Discussed here: https://groups.google.com/forum/#!topic/android-gcm/Y33c9ib54jY)
Depending on the browser being used, there are a few factors that determine if a notification can be received when the browser is not running.