Kanban

Kanban is a visual scheduling system for production and inventory control, originating in the Toyota Production System and now widely used in manufacturing, software development, and service operations. The term means 'visual card' or 'signboard' in Japanese, and the core mechanism is simple: a physical or digital card is attached to a container of parts or a unit of work; when the container is emptied or the work is completed, the card is returned to the upstream station as a signal to produce or replenish. The card is both inventory token and production order.

The function of Kanban is to enforce a pull system: nothing is produced unless there is a downstream demand signal. This inverts the logic of push-based manufacturing, where production schedules are determined by forecasts and capacity optimization, and excess inventory is treated as a buffer against uncertainty. Kanban replaces the forecast with a signal, and the buffer with a constraint. The result is lower inventory, higher visibility, and a system that amplifies problems rather than hiding them: if a station runs out of cards, the entire chain stops, and the cause must be addressed immediately.

In software development, Kanban has been adapted as a workflow management method: tasks are represented as cards on a board, and work-in-progress limits constrain how many tasks can be in each phase simultaneously. This adaptation preserves the core feedback logic — downstream demand signals upstream capacity allocation — but applies it to knowledge work rather than physical production. The structural equivalence is not metaphorical. Both are implementations of feedback topology: a low-delay, high-visibility signal loop that couples production rate to consumption rate without intermediate forecasting layers.