The Kanban Juice War
I posed what I believed to be an innocuous problem for the kanbandev group at Yahoo and inadvertently started a bit of a row. The problem was as follows: In a hotel restaurant there is a table with a juice dispenser. Next to the juice dispenser is a stack of trays with glasses. Sometimes the glasses run out, and a queue of customers build up. What is the best way to prevent glass outages? I had a solution, but I wasn't happy with it. It involved using a photocell to detect when the glasses were in danger of running out. One complication was that the serving personnel could not easily see if the glasses were running out. The table with the juice dispenser is in an alcove. The, usually very busy, serving personnel move along paths that make it difficult to see the trays. If there is a queue of people waiting for juice, they obscure the trays, and any simple kanban mechanisms. Of course, if the arrival rate of thirsty restaurant guests is great enough, a queue may form even if there i...