Buffer and flow at Caffè Artigiano

Caffè Artigiano not only does the best coffee in Calgary.  It also is a great demonstration of the use of a buffer and drum & rope from theory of constraints.  Below is a picture of the cafe:

And this is what it looks like drawn up:

In normal operations one of the baristas is the bottleneck.  And one the rules of theory of constraints is that the bottleneck has to be protected so that it can run at maximum capacity and therefore the whole system runs at maximum capacity.  The cashier is the other step in this process and does have occasional problems which we call Murphy's law.  Examples are credit cards not working or customers who forget their wallets or don't know what they want.  These would all stop the line if the cashier was at the end of the process, reducing the capacity of line.
The way the bottleneck is protected here is by moving the cashier to the start of the line.  When there is a delay at the cashier the buffer starts to get used up.  However the cashier is normally faster than the baristas and is easily able to catch up.  This means the baristas are never waiting for the cashier and more importantly we as customers are not caught waiting unnecessarily.
How does the drum and rope work is this situation.  The end barista and the cashier are linked both by a physical buffer and an electronic rope.  The physical buffer works like a kanban  in that it only lets a limited number of people into the space.  The buffer also maintains first in first out so the barista does not get overloaded.  The electronic rope is the till system which automatically tells the barista what the next coffee to make is.
So if you are in the mood for great coffee and an example of TOC/Lean in action Caffè Artigiano, 332 6th Avenue S is the place to go.