The correct way to deliver notifications is through push notifications. On mobile platforms it will wake up the device, wake up the app and handle the notification. No matter if your app is backgrounded, completely quit or open. It's actually really cool and efficient.

It's the low quality code from whatsapp and meta that's causing the battery usage doing all sorts of bad patterns like like constant outbound requests. So many apps like telegram don't have the same issues and are also just as responsive.