A Lesson We Learned: How We Stopped Negative Stock for Good
Based on the real development log, the TtaKkaa team faced a genuine problem: under certain conditions, a product could get sold even though its stock balance had actually hit zero. This usually happened when more than one sales channel (cashier and customer app) tried to sell the same product at nearly the same moment.
The problem: selling faster than stock updates
Picture a product with just one unit left in stock, and at nearly the same moment a customer orders it from the app while a cashier in the shop sells it to a customer standing in front of them. If the system doesn't verify the balance instantly before confirming the sale, both could go through, and stock ends up negative — the system claiming you have "negative one" unit, a number with no real meaning.
Why negative stock is a real problem, not just an odd number
Negative stock isn't just a strange number in a report — it means a store owner sold a product that doesn't actually exist, creating a real problem: a customer paid for something they won't get, or a cashier has to apologize to a customer standing right in front of them.
The fix: a sellability gate before confirming any sale
The TtaKkaa team built a sellability gate that runs before any sale is finally confirmed, regardless of the channel (cashier or customer app):
- The system verifies the actual stock balance at the moment of the sale attempt.
- If the balance isn't enough, the transaction is rejected instantly instead of being confirmed and causing a negative balance.
- If a product hits zero, it's automatically marked "temporarily unavailable" across every channel.
- For offline sales, the same check happens at the moment of syncing with the server.
A "stop list" as an extra tool
Alongside the sellability gate, the TtaKkaa team added a "stop list" that lets a store owner manually stop selling a product even if its stock balance exists, for cases like a quality issue with the product or a product reserved for a specific occasion.
The lesson learned
The lesson here: any system handling more than one sales channel at once must treat inventory as a single source of truth, checked instantly, not as a number updated afterward. The difference sounds simple in words but matters enormously in implementation.
If you want to learn more about inventory management on TtaKkaa
Read the story of a bakery managing its inventory accurately, and see how branch treasury complements this accuracy on the cash side, not just inventory.
Escrito por The TtaKkaa team
con el equipo Ttakka
Prueba Ttakka en tu negocio
Inicia una prueba gratuita y mira la caja Ttakka funcionando el mismo día.
Probar gratisPreguntas frecuentes
How exactly did this problem happen?
In busy conditions, or sales happening from more than one channel at the same time (cashier and customer app together), an item could get sold more than once at nearly the same moment before stock updated, pushing the balance negative.
Does this fix slow down selling?
No, the check happens in a fraction of a second and doesn't affect the cashier's or customer's experience while ordering.
If stock hits zero, what exactly happens?
The product is automatically marked 'temporarily unavailable' and can't be sold until stock is replenished, whether from the cashier or the customer app.