Syncing a wholesaler's API into WooCommerce without overselling or melting the server

A common WooCommerce brief looks like this: the store does not own its inventory. A distributor does. The shop is a storefront on top of a wholesaler whose catalog, stock levels, and prices change daily, exposed through some REST or XML web service. The job is to make the store reflect the supplier's reality automatically, and to never sell something the supplier cannot ship. We shipped exactly this for an automotive-parts store recently (client and supplier stay anonymous). Tens of thousands of indexes, a wholesaler REST API, and a hard requirement: no manual catalog work, and no orders for parts that are not actually in stock. Here is what the architecture looks like and the traps worth knowing before you start. The store is a view, the wholesaler is the source of truth The first mental shift is that WooCommerce is not the system of record for products. The distributor is. WooCommerce is a cache with a checkout attached. Once you accept that, the design falls out: a sync layer pulls from the supplier and writes into WooCommerce on a schedule, and you treat the WooCommerce product data as derived, not authored. The integration answers three questions, and you should answer them explicitly before writing code: What syncs - catalog, attributes, media, stock, price. Which direction - here it is one-way (supplier to store); orders stay in WooCommerce. How often - split it. Stock and price are cheap and change constantly, so poll them frequently. Full catalog and media are expensive, so refresh them rarely. Map fields declaratively, or you will rewrite it every month The supplier describes a product its way (its own index, EAN, attribute names, HTML description blobs, image URLs). WooCommerce wants its way (product, attributes, variations, media library). The bridge between them is a field map, and the single best decision we made was keeping that map declarative - a data structure, not a pile of if statements. When the wholesaler adds a new attribute, you extend the ma