I have recently upgraded my android app to FCM. Since then, the app initialization has slowed down. Its taking around 10-15 secs to show the splashscreen. Once initialized, the app is launching quickly upon further access. Also, the app has occupied ~15MB of data without any data saving from my end.
What could be the reason for this sluggishness and the data occupancy?
You could solve it by disabling Instant Run feature.
Instant Run need to add some files to work, so it tends to add our apk size.
Read More about Instant Run.