[pinars]

Distributed load balancing is a tough problem with two pieces to it. One is the queueing theory part.

The other is the systems side to it. If you have multiple customers and multiple checkout lines, and if your customers act independently without seeing the lines (no feedback from servers, network failures and delays, implementation complexity), what do you do?

It isn't a trivial problem. The easy route is paying Cisco's load balancers millions of dollars, but those only scale so far.

The bigger internet companies spend years of development time trying to make distributed load balancing work, but the issues there are a bit more complicated than a few customers walking to checkout lines.