Depends on what time you want to board. In June, I arrive at 11am for a 12.30pm boarding. At 11.15am, they started calling suite and privilege guests. Then people based on boarding time pretty much in 5mins interval or as much as the queues can take. After the paperwork, a number is written on your boarding paper. Suite and privilege guests will once again be called through customs first, before the numbers.
I was on board at 11.45am. This will differ each cruise.
If you opt to board later, say 1pm, I have read that there is pretty much no queues.