What began as a 30-day sprint for efeone turned into a 9-month journey to build an Amazon integration app for a high-volume seller on ERPNext and Frappe. The team navigated scope creep, shifting client expectations, evolving business models, and the quirks of Amazon’s APIs. Along the way, they re-architected the app multiple times, creating flexible workflows and API integrations to handle data inconsistencies, stock mismatches, and payment delays. The result was the Amazon e-Seller App—a scalable, reusable solution that syncs orders, payments, and inventory, automates operations, and offers clear multi-channel insights. This talk shares behind-the-scenes lessons on managing client pressure, adapting architecture, and delivering under unpredictable timelines. It’s as much about teamwork and persistence as it is about building robust, open-source marketplace integrations.