My old android device didn't have any inbuilt app locker software pre-installed on it. So I downloaded the 'App Lock and Gallery Vault' application from the play store.
After using for a week I noticed that my CV phone's battery never lasted longer because this app was running in background. It drained my battery so fast and I had to charge my mobile twice a day.
Also the app occupies some specific RAM of my device due to which my phone run a bit slower and sometimes it got hanged.
Moreover my phone got a little heated while this app was running.
The app also sometimes fails to recognize my fingerprint id and face id too. Then I had to unlock my apps using the security pattern only.