Double Queues for faster Delivery

Is your organization constantly overburdened?
Do you have an endless list of tasks, and nothing seems to get finished? Are you unable to predict how long it will take for that freshly arriving work item to get done?
Here's a simple tip: Set up a "Waiting Queue" before you put anything into progress.

The Wait Queue


The idea is as simple as it is powerful:
By extending the WIP-constraint to the preparation queue, you have a fully controlled system where you can reliably measure lead time. Queuing discipline guarantees that as soon as something enters the system, we can use historic data to predict our expected delivery time.

This, in turn, allows us to set a proper SLA on our process in a very simple fashion: WIP in the system multiplied with average service time is when the average work item will be done.
This allows us to give a pretty good due date estimate on any item that crosses the system boundary.
Plus, it removes friction within the system.

Yes, Scrum does something like that

If you're familiar with Scrum, you'll say: "But that's exactly the Product Backlog!" - almost!
Scrum attempts to implement this "Waiting Queue" with the separation of the Sprint Backlog from the Product Backlog. While that is a pretty good mechanism to limit the WIP within the system, it means we're stuck with an SLA time of "1 Sprint" - not very useful when it comes to Production issues or for optimization!
By optimizing your Waiting Queue mechanics properly, you can reduce your replenishment rate to significantly below a day - which breaks the idea of "Sprint Planning" entirely: you become much more flexible, at no cost!

The Kanban Mechanics

Here's a causal loop model of what is happening:


Causal Loops

There are two causal loops in this model:

Clearing the Pipes

The first loop is negative reinforcement - moving items out of the system into the "Waiting Queue" in front of the system will accelerate the system! As odd as this may sound: keeping items out of the system as long as possible reduces their wait time!

As an illustration, think of the overcrowded restaurant - by reducing the amount of guests in the place and having them wait outside, the waiter can reach tables faster, there's less stress on the cook - which means you'll get your food faster than if you were standing between the tables, blocking the waiter's path!


Flushing Work

The second loop is positive reinforcement - reducing queues within the system reduces wait time within the system (which increases flow efficiency) - which in turn increases our ability to get stuff done - which reduces queues within the system.

How to Implement

This trick costs nothing, except having to adjust our own mental model about how we see the flow of work. You can implement it today without any actual cost in terms of reorganization, retraining, restructuring, reskilling - or whatever.
By then setting the work you permit within your system (department, team, product organization - whatever) to only what you can achieve in a reasonable period of time, you gain control over your throughput rate and will thus get much better predictability into forecasts of any type.



Footnote:
The above is just one of many powerful examples of how #TameFlow deals with our pre-conceived mental models in order to enable us to create better systems - at no cost, with no risk.

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