Zero-Downtime ECS EKS Migration: Orchestrating a 6-Team Production Cutover at Scale

Task at hand: Migrating Live Healthcare Services Without Dropping a Single Request When you're processing healthcare revenue cycle transactions worth millions of dollars daily, downtime isn't just inconvenient—it's financially catastrophic and potentially impacts patient care. This is the story of how we migrated 15+ microservices from AWS ECS to EKS across 6 engineering teams with zero downtime, zero rollbacks, and zero production incidents. The stakes: AR Finance and Posting Modernisation serv