[API-users] did identifiers change btwn the old and new gbif?

It looks like http://www.inaturalist.org/observations/64364 is indexed at both http://data.gbif.org/occurrences/606641999 and http://www.gbif.org/occurrence/891075685. Does this mean the same records have completely different identifiers in the old and new systems? Additionally, do identifiers change every time an external source gets indexed, or was this switch just due to migration to a new data store? Please tell me they don't change on every index. I'm trying to use the API to check whether iNat observations have been indexed by GBIF and the link back to the GBIF version on each observation page. If the identifiers change, that means the links will break every time you re-index us.

-ken-ichi