[cameronh90]

Until last week I would have been confused by this, but last week my Pixel 4 broke.

While waiting for it to be repaired, I bought a cheap Chinese phone to use as a backup - not sure of the brand but it cost £200.

I don't know what the fuck they did to the operating system, but notifications are completely unreliable. I think there's possibly some aggressive app termination going on, maybe for battery or memory usage. Either way, most of the time I would only get a notification once I open the app. Some apps seem to be more reliable than others - maybe due to whitelisting as you say.

In hindsight, Google allowing these no-QA phones to use the Android branding was a big mistake.

[Too]

Killing idle apps, including Services, is a feature in Android to conserve battery life and to give memory to Activities in more recent use. This might not be as noticeable on high-end-phones.

A lot of shitty written apps are not aware of this and think they can run some while loop in the background to poll their own backend 10 times per second. Eventually that will get killed.

The solution to this is the push apis, or for apps that truly need a background loop to present a persistent notification aka "foreground-service", so the user is aware something heavy is going on in the background. Hearing FCM, which is the suggested push solution, having delivery issues above is not very comfortable.