Flew DEN-FRA-BCN yesterday. At BCN, walked off the plane, headed for the exit, you get to a area with green signs and rope (not really rope but I can't for the life of me remember what the extendable dividers for line management are called). I remember seeing a sign that said something like "fast pass" or "qr code". I told them I was arriving from the US with qr code on my phone in hand. They waived me through. At desk, the woman behind glass scanned my qr code and waived me through. Next stop was a temperature check I think. Stood on a "feet" sticker on the floor for half a second while they scanned and then was waived through into baggage area.

No lines or anything. I almost never stopped moving and was through in less than 30 seconds. My wife and I were the first off the plane and walk fairly fast, so that likely helped, but it was really seamless.