[wasyl]

While it's likely true, GCM/FCM is handled by Google Play Services, which is whitelisted and has I believe system-level permissions. It has less restrictions than a regular app exempt from battery optimisations, as it's supposed to be the only app that needs to run in order to coordinate things like push messages or location updates across all apps on the device

edit: I missed that the original post was talking about keep-alives and you were probably referring to them. But how app-level optimisations can help with keep-alives?