Uninstalling is not enough — Android Auto Backup silently restores your app data
From API 23 onward, Android backs up prefs, SQLite and cache to the user's Drive, then restores them on reinstall — before the app's very first launch.
This Android feature played a nasty trick on me. I uninstall the app, reinstall to start clean, relaunch. And there — surprise!
The first account's data was still there.
The culprit: Auto Backup.
How it works
As soon as your app targets API 23 or higher, automatic backup to the user's Drive is active by default. Without a single line of code. Prefs, SQLite and cache included.
So on reinstall, you don't get a fresh app. The system restores the latest cloud snapshot right after install, before the very first launch.
What to do
You can keep the backup but exclude what has no business being there (cache, tokens) via:
dataExtractionRules(API 31+)fullBackupContentbefore that
If you're still reading, I suspect you're about to go check your manifest. 😇