Part 8: Phase 3 — Full Cutover: Zero Downtime + ArgoCD GitOps
Phase 3 is the final act: 100% of traffic moves to microservices, Magento becomes a passive archive, and the platform runs entirely on Go microservices via GitOps. No PHP in the critical path. No Magento license renewal needed. Answer-first: Customer and Catalog services cut over at 100% immediately (they’ve been stable through all of Phase 2). Order Service uses a graduated 25%→50%→75%→100% ramp over 10 days, with a monitoring hold at each step. Magento stays alive as a hot standby for 30 days — an archive-service syncs microservice data to Magento hourly (one-way, for regulatory compliance). All deployments use ArgoCD + Kustomize; a git commit triggers a production deployment within minutes. ...