Explanation of the battery saving modes on Android

I am new to SyncThing and not that familiar with Android. Every time I open SyncThing I see a prompt to disable Android battery optimizations. What are the tradeoffs with choosing disabling battery optimizations? I have searched around but not found a clear explanation. It seems like Android will silently kill SyncThing under some conditions (no user interaction for a certain amount of time?). If that’s the case, will SyncThing never recover on its own, or only when I open the app again? What about if I use the sync only on wifi or only while charging options? Will those changing conditions revive syncing even if Android stops it for battery optimization?

Besides the Android optimization, I also see options to respect the Android battery saving setting, keep the CPU awake, and run service with foreground priority. How do these interact with each other and battery optimization? I assume I should leave them alone until I have problems.

My initial use case is to use SyncThing as send only on an Android phone to a laptop as a way to backup some apps. If it only synced once a day that would be okay with me, so I’m not too concerned about Android stopping syncing as long as it can restart some time over the course of a day.

Its basically like you said. If battery optimizations are enabled, Android may kill the app if its not in use. Opening the app manually will start it again. Triggering wifi/charging conditions should also start it again (though I have never really tested this).

Keeping CPU awake or running in foreground are useful if disabling battery optimizations is not enough, and the app is killed anyway. I suggest you only enable those options if you need them, as they may cause extra battery usage.