Search before design
On a distribution site, search is not a feature in the header. It is the product. A buyer arrives with a code, a specification, or a part they are trying to replace, and the site either resolves it immediately or loses the order to a phone call.
That means exact-match behaviour, tolerance for how codes are actually typed, cross-references from other manufacturers, and faceting on genuine engineering attributes. All of which depend on the catalogue data being structured — which is why these projects are usually product data work with a storefront attached.
The sales desk is the competitor
Your buyers already have a way to order: they ring someone who knows them. A website only displaces that if it is faster for the routine cases.
So the measure of success is not sessions or even conversion rate. It is whether the volume of routine calls — stock checks, order status, reorders, datasheet requests — has fallen three months after launch. If it has not, the site has not yet done its job regardless of how it looks.
Where this sits
This is B2B commerce at the demanding end, dependent on integration work because the ERP owns price, stock and lead time, and on product data because the catalogue is the asset. A customer portal usually ships alongside it.