we have a situation whereby occasionally we would receive 2 Ids (utilized also as subscriberKeys) for the same customer from another system. These records will have different PrimaryKeys (no violation thus) which are created automatically during sync times. Now, since this is an edge case, and we expect only a handful of records to end up in SFMC with the same Id /subscriberKey but different PK twice, I was wondering instead of making the existing audience automation more cumbersome and with lesser steps / faster, can we rely on the out-of-the-box settings in Journey Builder? In particular, if we set up Journey Builder to allow records to enter the journey only after exiting, and therefore skip duplicate subscriber keys during evaluation, will this make up for the alternative SQL intervention prior to JB (i.e. some form of PARTIION BY or GROUP BY)? I know this is not a problem in Email Studio due to the de-duplication on email address settings, but one-off campaigns will be rare with this audience. Thanks
In journey builder unique contacts are identified by having different contactKeys/SubscriberKeys. In your case the subscriberKeys are different and emailaddress is the same, this will be treated as 2 different subscribers. If you do allow re-entry after exiting for some cases you'll get subscribers that can exist in the journey multiple times due to each one having different subscriberKeys.
You should apply the dedupe SQL to avoid cases where within the same audience you can have multiple contacts with the same email. Why not just add a additional query before your journey runs to do the deduplication?
For better reporting and tracking purposes it would make sense for you to clean up some of those duplicate contacts or else you'll have tracking for emails being associated with 2 different contacts, and can be a issue when it comes to managing unsubs.