Reflow

Resale sellers juggle deal hunting, stock, listings, parcels and buyer messages, often in spreadsheets and a dozen tabs. Reflow starts with the deals: it watches new listings on nine marketplaces (Vinted, Leboncoin, Wallapop, Subito, Catawiki, Vestiaire Collective, Poshmark, eBay and BookVillage), alerts sellers to the ones that match their filters, and lets them act on a good one in seconds.

Behind the deal feed, it keeps their inventory, listings and orders in one place. I build and run it at Wavyzz, my company in Lille.