Weighted Shortest Job First - the Very Basics

This first post will introduce the topic of Weighted Shortest Job First and how this concept can be applied to most businesses.

Weighted Shortest Job First (WSJF) = High Numerator / Low Denominator

The numerator is value which we will first represent in dollar signs ( $ $) and the denominator is time.

WSJF helps your business if you can select work that has a high numerator over a low denominator. This is a fairly simple calculation that will maximize "Business Value" per work item.

Let's start with the very basics and talk about how to say it; "Wiss-Jiff". Ok, now we know how to pronounced it, so let's go even more basic and introduce "Siss-Jiff". I made up this concept when trying to explain the Lean Principals behind WSJF when folks were getting too hung up on defining the Numerator. So, let's just focus on the Denominator for now. Shortest Job First ( "Siss-Jiff") is the Denominator of the WSJF calculation.

Shortest Job First (SJF) = Time it takes to complete a specific Work Item.

That's it! That's "Siff-Jiff" (SJF) defined. Now, we have half the calculation of WSJF defined. Before we move on to the Numerator let's go through a grade school example of how this applies to a business work flow.

A pizza shop, a lemonade stand on the beach, a jewelry making assembly line out of a home, a home remodeling company, a multi-billion dollar supply chain and Information Technology and Software Development work flows.

All of these businesses have a few things in common:

1.) They all want to maximize the good and minimize the bad
2.) Each of them have limits or constraints on Time
3.) Each of them have work flows that also contain hidden "gotchas" - more constraints
4.) None of them can predict the future with 100% accuracy all the time
5.) All of them could make better "business" decisions in the face of change and uncertainty by applying WSJF

Let's pretend I am working a lemonade stand at the beach on a hot summer day. Let's also pretend that I can make 5 cups at a time without any problems. Each cup takes me 15 seconds to make and luckily for me everything is just perfect. 5 customers show up and 5 customers get their ice cold beverages with little to no wait times.

Cup Order Fancy Numerator Time per Cup (SJF)
Cup 1 $$$ 15 Seconds
Cup 2 $$$ 15 Seconds
Cup 3 $$$ 15 Seconds
Cup 4 $$$ 15 Seconds
Cup 5 $$$ 15 Seconds

This is great! I'm making cash selling lemonade at the beach! And, everything is 100% easy and perfect.

Yeah, you know what is coming next - a thunder storm. We are at the beach after all. This thing moved in fast and knocked out most of my supplies. It moved out of the area as fast as it came. But, I have a slight problem (enter our first constraint!) - I now have to move about the stand in such a way that changes my denominator because the storm upset my "normal" work flow.

Cup Order Fancy Numerator Time per Cup (SJF)
Cup 6 $$$ 15 Seconds
Cup 7 $$$ 30 Seconds
Cup 8 $$$ 20 Seconds
Cup 9 $$$ 45 Seconds
Cup 10 $$$ 25 Seconds

Now, we can see that a bit of Randomness entered my perfect stable work flow post the afternoon thunderstorm at the beach.

Lines are starting to form at my stand. In the back of my mind, I am wondering if I should adjust my price per cup (the Fancy Numerator) to cover the extra labor time per order? Well, that doesn't feel fair to my customers, so I decided to just finish the rest of the day the best I could and left the price the same.

Part II of the WSJF Basics will add more constraints to our beach example which means we are going to make adjustments to the Numerator.

Thanks for reading and stay tuned!