Marketplace integration is usually bought on its own and only afterwards connected to the ERP. Reversing that order hurts a lot less.
01. The Layers
There are four layers: marketplace, integrator, ERP and warehouse. What each layer owns must be written down up front. The ERP may own product definitions, the WMS stock, the integrator orders; but nothing should have two owners.
02. Product Flow
Products are created in the ERP, sent to the integrator and distributed to channels from there. Creating products by hand in the marketplace panel is fast in the short term and produces mapping chaos in the long term.
03. Order Flow
An order moves from the marketplace to the integrator and lands in the ERP as a sales order. The ERP passes it to the warehouse as a work instruction. After shipping, information returns along the same chain.
04. Is a Middle Layer Needed
If your ERP can connect directly to the integrator's API, no middle layer is needed. If it can't, a light intermediate service handling transformation and queuing solves the problem without polluting the ERP.
05. Multiple Warehouses
If different channels ship from different warehouses, the warehouse assignment rule must be defined inside the integration. Manual assignment afterwards quietly raises shipping cost.
06. Traceability
The marketplace order number, the ERP order number and the shipment number must be linked. Being able to follow the chain end to end shortens support time when a complaint arrives.