Syncing ERP stock with a B2B webshop: cost and architecture

The verdict in three sentences

Wrong stock on a B2B webshop costs more than having no webshop, because every order cancelled for a stockout damages the relationship with a professional buyer who orders every month. The right architecture combines API sync every 5 minutes, stock reservation at the moment of the order and a discrepancy log the warehouse team can read. For an 8,000 SKU catalogue, plan on 6 to 10 weeks and a connector that falls into a simple or medium custom application, with a measurable payback in under a year.

Why displayed stock is wrong two to three times a day

Take a distributor based in the Spandau industrial area of Berlin, selling abrasives, fasteners, PPE and tools to around 1,400 active accounts: workshops, automotive subcontractors, construction firms across Brandenburg and a few customers in Poland. The ERP handles receipts, picking and stock counts. The webshop receives a CSV export overnight, then a manual update around noon.

Between exports, three flows change stock without the webshop knowing: trade counter sales, orders phoned in to sales reps and supplier returns. An item shown as 42 in stock may in fact have 3 left. Across 8,000 SKUs, it only takes 150 fast movers to be affected to generate several impossible orders every day.

The architecture that holds up

Three building blocks cover most distributors. The first is a connector that calls the ERP API every 5 minutes and only pulls SKUs changed since the last run. On 8,000 items that is often fewer than 300 lines per cycle, a negligible load for the ERP.

The second is stock reservation. As soon as a buyer confirms the basket, the webshop sends a reservation to the ERP for each line. If the ERP replies that the quantity is gone, the shop immediately offers a backorder, a restock date or an equivalent SKU. The buyer no longer discovers the stockout in an email two days later.

The third is the discrepancy log. Every gap between displayed stock and ERP stock is recorded with SKU, time and likely source. After a month, the team knows whether the problem comes from counter sales, returns or a badly configured secondary warehouse.

At Kolonell, this kind of connector is a simple custom application, FCFA 2,500,000 to 4,000,000 (EUR 3,810 to 6,100), or a medium one, FCFA 4,000,000 to 7,000,000 (EUR 6,100 to 10,670) once you add several warehouses, customer-specific prices and fine backorder rules. Maintenance then runs from FCFA 35,000 to 120,000 per month (EUR 53 to 183) depending on the support level.

What to check before you sign

Does the ERP have a documented API, or do you need an intermediate database? Most current ERPs used by German and Dutch distributors offer a REST API, but older versions can only export files. In that case the connector reads an exchange folder every 5 minutes, which is still far better than a nightly CSV.

Also decide who owns the data. The ERP must remain the single source of truth for stock and net prices, the webshop only displays them and creates reservations. Finally, plan a sync status page: the team should see at a glance when the last successful run happened.

Mini case study

Jonas, sales director at the Berlin distributor, handles about 2,600 online orders a month with an average basket of EUR 380 excluding VAT. At 4% stockout cancellations he loses 104 orders a month, close to EUR 39,500 of deferred or lost revenue. If only half is truly lost, that is about EUR 19,750 per month.

After moving to a 5 minute sync with reservation at checkout, the rate drops to 0.8%, or 21 orders. The monthly gain is about 83 orders, roughly EUR 15,800 of revenue preserved under the same half-lost assumption. At a 28% gross margin, that is about EUR 4,400 of margin per month. A medium-level connector at EUR 7,000 pays for itself in under two months, before counting the customer service hours freed up.

FAQ

Does syncing every 5 minutes overload the ERP? No, as long as the connector is delta-based and only requests changed SKUs. On 8,000 items you usually process fewer than 300 lines per cycle, a few seconds of work.

Do we need full real time? Rarely. Between 5 minutes and real time, the difference in cancellations is often under 0.3 points, while webhooks require a newer ERP and more testing.

What happens if the ERP goes down? The webshop keeps showing the last known stock and flags orders as awaiting confirmation. When the ERP returns, reservations are replayed in order, usually in under 10 minutes.

How long does the project take? Plan on 6 to 10 weeks for 8,000 SKUs, including acceptance and phased go-live. An ERP without an API often adds 2 weeks.

Isn't an off-the-shelf iPaaS enough? It can be if both ERP and shop have standard connectors, at EUR 300 to 1,500 per month as a 2026 ballpark. Once you need customer-specific prices and backorders, custom often wins over 3 years.

Let's scope your project. We audit your ERP, your webshop and your stock flows, then scope a connector delivered in 6 to 10 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.