Whenever you have a work in progress (which, of course, you wind up with lots of WIPs when you multi-task) you’re creating waste. In the world of physical manufacturing the problems of WIPs are perhaps more obvious – the added cost of inventory/storage and the risk that if a product line changes/stops production, all that WIP is just throw away. But, he says, in software development the costs and risks associated with having all these outstanding WIPs are even worse. Knowledge degrades quickly, requirements get out of date, the feedback loop is delayed so we don’t learn what we’re doing wrong. Not to mention all that half-done/probably untested code intermingled with our production code – some of which we never get a chance to get back to, so it’s just degrading our product.

Next time I go on an interview, I think I’ll prefer the company that asks YOUR question.