I know storage is cheap, but I think you run into storage space issues very rapidly if you want high-definition, 24/7 surveillance of every apartment building stretching back weeks.
Storing video footage from weeks back does not seem feasible. I assume footage would get overwritten after a specific time period.
Store hashes of the detected faces. Or store low framerate video, just occasional frames where people are detected
It doesn’t need to store video, just data about where the person is and there various identifying data… the system uses the recordings to generate fingerprints for everyone, then just stores data about where you were/are.
until someone finds that certain cameras are unavailable, or that something has obstructed the view for a significant enough time to cause reasonable doubt