I was surprised too! When getting the marriage license I asked them how long we would have to wait for the marriage certificate and that's when they told us we would be able to take it home the same day if we did it there. It is issued by the county, signed by the deputy clerk who did the ceremony with us.
They also explained that the long waiting time mostly happens because of how long it takes couples to hand in the marriage license after their ceremony and mailing times. Once they receive it, they register it in the county records and that is done very quickly.
Sorry, if I'm not using 100% correct terms, I hope you understand what I'm saying 🙂