One unit of stock can be sold twice when the storefront and the till each believe they are holding it, and connecting Shopify and Lightspeed POS decides which location is actually holding it.
A shop with a storefront and a shop floor is selling one pile of stock through two doors. First the website sells the last one, then somebody carries it to the counter, and the customer who ordered online gets an apology two days later. The usual answer is a stock count reconciled between the two, which is accurate for exactly as long as it takes somebody to sell something. Connecting Shopify and Lightspeed POS makes each location's own position the figure both sides sell against, so the last unit is sold once by whichever door reaches it first.

A sale at the till moves the Shopify position for that location, so the website stops offering something that walked out of the door twenty minutes ago under somebody's arm.
Each shop has its own figure rather than a share of a pooled one, so a customer choosing collection is choosing a branch that actually has the thing they came for.
The reconciliation between shop and store is no longer what keeps both honest, so counting becomes a check on the figures rather than the mechanism that produces them.
A return taken at the till puts the unit back in that shop's position, so the stock comes back where it physically is rather than into a total nobody can act on.
When something sells at a Lightspeed POS till, Alumio updates the Shopify position for that location, so the website is selling against what is left in the shop rather than against the figure that was true this morning.
When a shopper chooses collection, the Shopify page shows the branches that hold the item, and taking that unit out of the chosen location is what keeps the next shopper from being offered the same one an hour later.
When a customer brings something back to a shop, the unit re-enters that location's position, so it becomes sellable again in the place where somebody can actually hand it over rather than inside a pooled total.
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A loyalty scheme is the third that changes the experience, and the reason is the same one. The customer who buys online and returns in store is one person, and the scheme only knows that if both sides say so. Alumio holds that connection alongside this one, so the points earned at the till and the points earned online belong to the same person rather than two.
Yes, and per location rather than as one figure is usually the point. A single pooled number is easy and tells a shopper nothing about whether they can collect today. Alumio keeps each location's position on both sides on the schedule you set. What can be written is whatever Lightspeed POS exposes for it, so that is confirmed first.
No. What changes is that the stock count stops being the thing holding it together; what does not change is that somebody still counts, because a shop floor loses units in ways no system sees. The mapping between a Shopify product and a till item is an entry you can read. Where a product is structured differently on the two sides, the Code Transformer handles that step.
In a location, which is the whole answer and the reason a pooled figure causes the problem. A unit is in a shop or in a warehouse, and both the website and the till are asking about the same physical thing. Once each location carries its own position, selling it is a question of which door reached it first, and the other door stops being able to offer it.
The visible failure is one unit sold twice, and the customer finds it before the business does. Alumio names the location the unit was held at and the sale that could not be applied, so the exposure is a specific shop rather than a general worry. Each update is monitored live and logged, a refusal alerts with the reason, retries run where configured, and nothing is lost quietly.
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