Just in time (JIT) is a production and supply system that aims to have only what's needed, in the quantity needed, at the moment it's needed — eliminating inventory that doesn't add value. It was developed at Toyota in the mid-20th century as part of its production system, and became the global reference for lean manufacturing.
It's one of the most searched logistics concepts. It's also one of the most misapplied when it moves from a factory to an online store.
How it works where it was born
In a plant running just in time, inventory doesn't pile up "just in case." Each workstation pulls from the previous one only what it's about to use, usually through a physical or digital signal called kanban (Japanese for "card"). Suppliers deliver several times a day, in small quantities, straight to the line.
It works because three conditions hold:
- Demand is known in advance. The plant knows how many cars it will build tomorrow: its production schedule is the demand.
- Suppliers are close and reliable. A delivery two hours late stops the line, which is why suppliers set up around the plant.
- The flow is stable. Same process, same sequence, every day.
When any of the three breaks, the system stops. That's the price of having no buffer.
Why e-commerce almost never meets those conditions
Put the same three conditions in front of a brand that sells online:
| JIT condition | In a plant | In e-commerce |
|---|---|---|
| Known demand | The production schedule | Whatever thousands of customers decide to buy today |
| Close, punctual supplier | Located next to the plant | Often in another state or another country |
| Stable flow | Same daily volume | Peaks for Hot Sale, Buen Fin, Christmas |
| Promise to the customer | Deliver to the next process | Ship today or tomorrow |
The underlying difference is the last row. An online shopper expects the order to ship today. If the product isn't in the warehouse when they buy, there's no way to "order it just in time": the sale is already lost, and on a marketplace it also costs you ranking.
For a brand that imports into Mexico, the problem grows. A container's lead time is measured in weeks and includes a customs leg no one controls: on September 14–15, 2026, a failure in Mexico's tax authority systems halted customs clearance for two days. Running without inventory on that chain is betting nothing ever goes wrong.
What you can borrow from just in time
Pure JIT not fitting doesn't mean the method is useless. Three ideas transfer well:
- Replenish often, in small lots. Instead of one big purchase every three months, more frequent orders lower average inventory and the risk of being stuck with product that stopped selling. It only works if your supplier accepts it without penalizing you on price.
- Measure real lead time. JIT forces you to know exactly how long each link takes. Even if you don't run JIT, that number is what makes your safety stock work.
- Treat idle inventory as a problem. JIT philosophy sees excess inventory as waste that hides other problems. A SKU that hasn't moved in six months is tied-up capital, not an asset.
And there's one case where something very close to JIT does work in logistics: cross-docking, when incoming goods already have a destination and are reshipped without being stored.
The middle ground: JIT where you can, buffer where you must
The practice that works for most brands is segmentation. With ABC inventory classification you separate the products that drive your sales from the long tail, and apply a different rule to each group:
| Group | Supply rule |
|---|---|
| Top sellers with a reliable domestic supplier | Frequent replenishment, close to JIT, with small safety stock |
| Top sellers, imported | A wide buffer, already cleared through customs; JIT is a risk here |
| Long tail | Less frequent purchases and periodic review of idle stock |
Frequently asked questions
What does just in time mean? Producing or receiving only what's needed, in the quantity needed, when it's needed, to keep inventory to a minimum.
Who created just in time? It was developed at Toyota as part of the Toyota Production System, starting in the 1950s.
What's the difference between just in time and kanban? Just in time is the goal: having what's needed at the moment it's needed. Kanban is one of the tools to get there: the signal that says when and how much to replenish.
Can an online store operate without inventory? Only with models where someone else holds the product, like dropshipping, and accepting less control over delivery times. If you sell and you ship, you need inventory on hand.
Just in time teaches you not to hold what you don't need; e-commerce requires having on hand what the customer will order today. Balancing the two is an inventory decision — and where that inventory lives is a warehouse decision. Ecommex stores and controls inventory for e-commerce brands so that replenishing often doesn't mean running out — see our warehousing service.