Jeff,

Check the archive there are several check out lane analogies that I have
posted.

I agree that the Queue is sub optimal, but it is more sub optimal the
smaller you are.  When you get to 50 instances it is amazing how well the
load balancing works.  On the climb up to peak new instances spin up on
requests rather than causing cascading failures or dramatic spin ups. And on
the way down instances de-utilized and end of life gracefully.

Using your grocery store analogy, imagine that you are optimizing for a
guarantee that you will be checked out with in 30 seconds of entering the
queue. The ideal scenario is that when you get to a spot where you know you
are 15 seconds from being checked out, and it takes 15 seconds to "open a
new lane" you want to send users to go stand in line while the register
opens.

Your goal is to never have to pay on that guarantee, not to serve the
highest percentage in the least time.  When this is your ideal QoS the
current load balancing does really well. It does better if it has 10
registers and can open 2 at a time, rather than when it has 1 register and
needs to decide if it is going to double capacity.

-Brandon


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