After watching ecommerce sellers lose money to oversells, I built Nventory — a multichannel order and inventory management platform. The core challenge: multiple marketplace APIs (Amazon, Shopify, eBay, WooCommerce) each maintaining their own inventory state, all drawing from the same physical stock. Polling every 15 minutes sounds fine — until a demand spike oversells you across three channels simultaneously. The fix is event-driven. Every sale fires a webhook that decrements stock across all channels within seconds. No lag, no oversells. Three things I didn't expect:

Every marketplace handles webhooks differently — reliability and payload structure vary wildly Simultaneous sales on different channels hitting the same SKU need atomic DB operations AI shopping agents now read real-time stock levels and can spike demand with zero warning

If you're building in ecommerce infrastructure or dealing with distributed state across APIs, check out what we've built at https://nventory.io/us — happy to discuss the technical decisions behind it.