How can I send notifications to Android devices in Doze / power saving mode?

Doze mode and App Standby may temporarily suspend background execution for your app when it goes to background or if the phone is idle.

To send notifications to Android devices in power saving mode, we recommend implementing FCM high priority fallback delivery. Pushy will attempt to deliver your notifications through MQTT and Firebase Cloud Messaging simultaneously, to burst through the various Android power saving modes.

Otherwise, you can ask your users to disable battery optimizations for your app by displaying an in-app dialog with instructions and firing the ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS activity (completely safe and will not get your app suspended from Google Play):

The code for displaying this dialog is as follows:

// Android M (6) and up only
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
    // Get power manager instance
    PowerManager powerManager = (PowerManager) getSystemService(Context.POWER_SERVICE);

    // Check if app isn't already whitelisted from battery optimizations
    if (!powerManager.isIgnoringBatteryOptimizations(getPackageName())) {
        // Get app name as string
        String appName = getPackageManager().getApplicationLabel(getApplicationInfo()).toString();

        // Instruct user to whitelist app from battery optimizations
        new AlertDialog.Builder(this)
                .setTitle("Disable battery optimizations")
                .setMessage("If you'd like to receive notifications in the background, please click OK and select \"All apps\" -> " + appName + " -> Don't optimize.")
                .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        // Display the battery optimization settings screen
                        startActivity(new Intent(Settings.ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS));
                    }
                })
                .setNegativeButton("Cancel", null).show();
    }
}

Either of these solutions (FCM fallback and/or whitelisting from battery optimizations) will make it possible for your users to receive notifications with your app in the background, even in power saving mode.