A kanban (Japanese for "signal card") is a visual token that authorises work. When you have a kanban, you produce or replenish. When you don't, you stop. It's how pull systems are implemented in real factories and offices.
Two kinds
- Production kanban: signals a station to make more of a specific item.
- Withdrawal kanban: signals a station to pull material from an upstream station.
The rules that make it work
- No kanban, no work. Even if you have capacity, you don't produce without a signal.
- Number of kanbans = max WIP for that item. Fewer kanbans = tighter flow.
- Kanbans move with the physical (or virtual) work item.
- Empty containers or slots ARE the signal, not paper cards. Modern kanban is often just marked-out floor space.
Digital kanban
The software team version - Trello, Jira, Linear boards - is a direct application of the same idea. Cards move through columns. WIP limits per column keep the flow smooth. If a column is full, nothing new can enter it until something leaves.