The special terminal they have for the Oasis/Allure is laid out specifically to handle boarding 6000+ passengers seamlessly. You do have to go through a real person to check-in but they have something like 90 check-in lines. People are staged all along the way, from the entrance to the terminal to the entrance to the ship. They are well trained and empowered to make things happen. It is typical to go from dropping your luggage off to boarding the ship in 10 minutes. Their standard is to not let it take more than 15 minutes no matter how many people are arriving.
You do everything including the security photo at the check-in desk. Very impressive operation.
Of course, you'll need to do your on-line check-in and you can do that any time after the booking is made. I did the online check-in for our June cruise two months ago.