The Lean Startup - Eric Ries [80]
When I work with product managers and designers in companies that use large batches, I often discover that they have to redo their work five or six times for every release. One product manager I worked with was so inundated with interruptions that he took to coming into the office in the middle of the night so that he could work uninterrupted. When I suggested that he try switching the work process from large-batch to single-piece flow, he refused—because that would be inefficient! So strong is the instinct to work in large batches, that even when a large-batch system is malfunctioning, we have a tendency to blame ourselves.
Large batches tend to grow over time. Because moving the batch forward often results in additional work, rework, delays, and interruptions, everyone has an incentive to do work in ever-larger batches, trying to minimize this overhead. This is called the large-batch death spiral because, unlike in manufacturing, there are no physical limits on the maximum size of a batch.6 It is possible for batch size to keep growing and growing. Eventually, one batch will become the highest-priority project, a “bet the company” new version of the product, because the company has taken such a long time since the last release. But now the managers are incentivized to increase batch size rather than ship the product. In light of how long the product has been in development, why not fix one more bug or add one more feature? Who really wants to be the manager who risked the success of this huge release by failing to address a potentially critical flaw?
I worked at a company that entered this death spiral. We had been working for months on a new version of a really cool product. The original version had been years in the making, and expectations for the next release were incredibly high. But the longer we worked, the more afraid we became of how customers would react when they finally saw the new version. As our plans became more ambitious, so too did the number of bugs, conflicts, and problems we had to deal with. Pretty soon we got into a situation in which we could not ship anything. Our launch date seemed to recede into the distance. The more work we got done, the more work we had to do. The lack of ability to ship eventually precipitated a crisis and a change of management, all because of the trap of large batches.
These misconceptions about batch size are incredibly common. Hospital pharmacies often deliver big batches of medications to patient floors once a day because it’s efficient (a single trip, right?). But many of those meds get sent back to the pharmacy when a patient’s orders have changed or the patient is moved or discharged, causing the pharmacy staff to do lots of rework and reprocessing (or trashing) of meds. Delivering smaller batches every four hours reduces the total workload for the pharmacy and ensures that the right meds are at the right place when needed.
Hospital lab blood collections often are done in hourly batches; phlebotomists collect blood for an hour from multiple patients and then send or take all the samples to the lab. This adds to turnaround time for test results and can harm test quality. It has become common for hospitals to bring small batches (two patients) or a single-patient flow of specimens to the lab even if they have to hire an extra phlebotomist or two to do so, because the total system cost is lower.7
PULL, DON’T PUSH
Let’s say you are out for a drive, pondering the merits of small batches, and find yourself accidentally putting a dent in your new 2011 blue Toyota Camry. You take it into the dealership for repair and wait to hear the