Express boarding usually works OK. Air Asia have gotten better at making sure the express boarders do get on first.

Air Asia boarding at CGK is almost always via a bus and express boarders board the bus first and sit up the front. When the bus gets to the plane they only open the front door of the bus to allow express boarders to get on the plane first.

If you are quick on your feet there isn't really much advantage to this service. I have never used it but I almost always get the seat I want anyway (row 1).

If you do decide to do it make sure you are right by the gate when the flight is called because they will only call you once or twice before starting general boarding.