Walk-ins wait for at least 3 hours!
They are so busy and seems like that makes them kinda rude to people who have no idea what is going on. I was waiting and watching the attitude of the staff to old people who are not familiar with the procedures. They cannot make you appointment so you can come back but you can make appointment online while waiting :)
You can literary die while waiting if you are walk-in.
Even people with appointments wait about 30 minutes.