The phrase that ruins every eCommerce project: "Just connect it to our ERP."

ECommerce projects routinely underestimate the complexity of integrating new storefronts with legacy ERP systems, often dismissing it as a simple task despite the fundamental architectural differences between greenfield storefront development and brownfield system integration. The integration layer fails because no single owner manages the handoffs between multiple systems (payment gateways, tax engines, inventory, accounting, CRM), creating unowned seams where systems designed in isolation must agree on data in real-time, leading to failures when unexpected edge cases occur.