I have no idea when the double-queue system started
But I knew there're places with such system that make people queue twice for their order

MacDonalds is one

I kept asking myself
If double-queue system benefits from anything

MacDonald's system so far is still ok
I have not much complaint about it
Other than the fact that I have to queue again on the left for the 2nd time after my order on the right
& also wait again for extra few minutes if the order in front of mine is not completed

Why the hassle?
Previously it was doing fine
Counter-staff took orders & grabbed the food from shelves almost immediately
That is because they knew what we wanted & the orders were still within their few seconds of memory
However
Having to get another staffs to grab the food
Time is needed to read the receipt over & over to confirm accurate order
That's exactly where the extra time is wasted

So what if orders are taken in first & not getting the food fast enough?
Is there efficiency?

In situation where there's no receipt
For example, my school canteen which I really hate
Food sucks & only the Western food store can make it
The queue is always damn bloody long on both lanes
& I calculated that I needa wait for 20mins for my food on the tray

Orders are taken verbally
& after that, you just head to the left side for the food

Apparently
I ordered 'Chicken chop, take away'
& I saw the guy told the chef behind him
Assuming orders taken
I headed to the left lane
When it's my turn to collect
He gave me a plate of Chicken Chop with Spaghetti

I told him I wanted Take-away
He blamed me for not telling him in the first place
So he told the chef to pack
& the chef packed Spaghetti in
& I quickly told him Chicken chop ONLY
He gave me THOSE kinda look

I was kinda pissed
As I'd expect a nice lunch after craving for Chicken Chop for a few days
I did mention my order correctly
But this double-queue system just make me sick in placed where orders are taken WRONGLY

In fact
This is not the first time I'd encountered this

So what is the efficiency of this double-queue system?
I prefer to wait just 5 minutes for my food
Instead of 20 minutes
Additional 5 minutes for correction of wrong orders