Key? No thank you.
The last flat I lived in (not long ago) had a much better solution. Normal keys to the (four) individual flats, but for the front door to the building, an oldfashioned mechanical combination lock. No question of tracking, but also without the inconvenience of a lump of metal to burden the pocket.
Security worked surprisingly well too: on at least two occasions, yobs tried and failed to get in.
 That's "apartment" to Leftpondians.