Hi! I answered this in the other post, but the Postgres UPSERT was the key. By using a combination of attributes (It may have just been name & D.O.B), In a single operation I could figure out if the cat has been posted (and update the existing row), or create a new row.

This worked as there were only ever 30-50 cats online at one time. If it was a thousand, I'm not sure what I would have done.

Edit: I realise now this was a rhetorical question. Oops!