Direct answer. Just-in-time (JIT), or "juste-à-temps" in French, is a flow-management method aimed at producing or supplying exactly what is needed, at the moment it is needed, in strictly sufficient quantity, without building up extra "just in case" stock. Popularized by Toyota, it stands in contrast to the traditional logic of stockpiling large quantities in advance.
A principle born at Toyota, applied across the whole chain
Just-in-time is one of the pillars of the Toyota Production System (TPS), the origin of lean manufacturing. The central idea is to synchronize every stage of production or delivery with the actual demand of the next station or customer, rather than producing ahead of time based on forecasts. In practice, a production station only receives its components when it actually needs them, and a warehouse only restocks a point of sale when triggered by a real order.
Kanban is the signaling tool most closely associated with just-in-time: it is what actually triggers the replenishment order at the right moment. Takt time, for its part, sets the pace at which production must proceed to stay synchronized with demand. In in-plant internal logistics, the milk-run is a typical application of just-in-time: a scheduled route delivers line-side stations only at the intervals needed, with no local overstocking.
Done well, just-in-time strongly reduces tied-up stock, the storage space required and the risk of obsolescence. Its main limitation is sensitivity to disruptions: a supplier shortfall or a transport incident can have an immediate impact on production, for lack of a buffer stock. Many companies therefore strike a balance between strict just-in-time and a limited safety stock on the most critical items.
FAQ
What is the difference between just-in-time and lean flow?
The two terms are very close and often used as synonyms in France. "Lean flow" (flux tendu) emphasizes the absence of buffer stock between steps, while "just-in-time" emphasizes precise synchronization between production or delivery and actual need.
Does just-in-time increase the risk of stockouts?
Yes, that's its main limitation: by reducing buffer stock, it exposes operations more to supplier or transport disruptions. That's why it is often combined with a targeted safety stock on critical items rather than applied uniformly across all items.
Related terms
Kanban · Lean · Takt time · Milk-run · Push flow / pull flow · Safety stock · Scheduling.
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