Experience is what you get when you didn’t get what you wanted. I learned that lesson the hard way as a junior consultant, fresh out of university.

One day, a bunch of specifications for a planning solver landed on my desk. Basically, a solver is an automated resolution of a given problem, in this case a particular supply chain planning challenge. In my enthusiasm as a junior, I was more than happy with these specifications and immediately began writing the required mathematical model. Of course, that involved a lot of x’s and y’s, the fundamentals of math vocabulary.

Horrified by the solver’s impact

A few weeks later, I demonstrated the result to the customer for whom it was meant. I was proud because the model acted exactly as prescribed, producing a great master plan that optimizes bucket volumes while reducing setup costs. Or that’s what I thought.

To my surprise, my customer was a little bit horrified when he spotted the impact on his inventory positions. Safety stocks were shrinking back, producing a high risk on stockouts. He asked me to undo all my work and forget about reducing the setup costs. Which made me ask the most important question: why? Why had he specified reducing setup costs in the first place?

Avoiding misunderstandings

It turned out to be a misunderstanding: setup reduction was an execution-level requirement, but it was largely irrelevant at master planning level where safety stocks were of greater importance for my customer.

Lesson learned: I had failed to ask the crucial why? questions before beginning to develop. It’s never happened again since that day. I now always put the why’s before the y’s.

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