Eyrix — Blog
FEFO and batch traceability: build it into the plan, not after the fact
In pharmaceuticals, food and chemicals, traceability isn't paperwork you tidy up afterwards — it's a condition of being allowed to produce at all. Every finished lot has to trace back to the batches it was made from, and stock has to be consumed in the right order so nothing expires on the shelf. Yet in most planning setups both of these are bolted on after the plan is built: FEFO is managed by hand at the warehouse, and lot genealogy is reconstructed when someone asks for it. Both are risks, and both come from the same root cause — the plan treats inventory as a number.
On-hand isn't a number, it's a set of lots
The moment shelf life matters, "500 units on hand" is the wrong model. What you actually have is a set of lots, each with its own quantity and expiry date. That single change reaches into the whole plan:
- Demand is met earliest-expiry-first. FEFO stops being a warehouse habit and becomes part of the calculation — each requirement draws down the lots that expire soonest and are still valid on the date they're needed.
- Expiring stock changes the plan. Demand that can't be met from stock with enough remaining shelf life generates a real requirement, even when the total on-hand number looks sufficient. A plan that ignores this quietly assumes stock it can't legally use.
- Batch size is capped by shelf life. A lot-sizing rule that would build ninety days of supply of a thirty-day product has to be clamped, or the plan schedules its own write-off.
Projected write-off is a result worth having
Once the plan ages lots forward through the horizon, it can tell you something no after-the-fact record can: which stock is going to expire unconsumed, and when. "You're on course to scrap €40k of product in week 11" is often the single most valuable line the system produces — a number you can still act on, weeks before it becomes a loss instead of a warning.
Traceability the plan can answer on its own
The other half is origin. When lot genealogy lives in the planning model — every finished lot carrying the chain of batches that produced it — an auditor's question is answered from the plan itself, with zero reconstruction. That's the difference between traceability as a scramble and traceability as a property of how you plan. It's also why a plan that respects finite capacity and lot expiry together is worth more than two systems stitched together after the fact.
The discipline generalises
This grew out of regulated production, where the rules are strict enough that there's no other way to do it. But the discipline — demand, capacity and sourcing decided together, with traceability built in rather than added afterwards — pays off wherever stock expires or a batch has to be accounted for. Regulated or not, a plan that knows what it's made of is a plan you can stand behind.