Definition
Inventory of controlled parts used for production into upstream processes.
In detail
Supermarket inventory is a controlled, limited quantity of WIP or raw material inventory placed at specific points in the production flow to transmit production instructions to upstream processes and buffer supply-demand fluctuations. It addresses the scheduling problem of "when to produce and how much to produce" in a pull system, triggering replenishment through visual inventory levels, avoiding overproduction and stockouts. Unlike a regular warehouse, supermarket inventory serves internal customers (downstream processes), and each part has defined maximum and minimum inventory levels, following FIFO principles. Typical outputs include replenishment kanban or production instructions, as well as data for calculating safety stock and batch sizes.
Example in practice
Next to an assembly line, there was a parts supermarket where each part was stored at a fixed capacity. When downstream workstations took parts, supermarket inventory dropped to the replenishment point, and a water spider carried a kanban to the upstream processing cell, instructing it to replenish the corresponding quantity. This ensured continuous assembly line operation while avoiding upstream overproduction. After use, on-site inventory levels became visible, replenishment rhythm stabilized, and scheduling basis was clear, reducing waiting and backlog caused by information lag.