When the recorder performs a reverse geo lookup for a particular lat/lon (a.k.a. geohash) combination we store the address (and since recently tzname) in the database.

In the course of time, that address might be invalidated, e.g. a street is renamed. (It's even possible that a time zone is renamed.)

The proposal is to add something like a ttl to the cached data and periodically purge expired entries.