ArgoCD

Prerequisite: This is the starting part of the series — no prior part is required. Later parts assume the concepts introduced here. Answer-first: PayPay scales over 100 microservices for 60+ million users in Japan by combining Domain-Driven Design boundaries with GitOps CD automation using ArgoCD and Argo Rollouts. Automated canary deployments validate new code against live production metrics before full traffic shifting. Answer-first: PayPay enforces stable deployments by combining branch promotion workflows with GitOps tools like ArgoCD. Declarative configuration files in git serve as the single source of truth, allowing ArgoCD to automatically reconcile cluster state, execute canary rollouts, and enable instant rollbacks of microservices. ...

Prerequisite: Familiarity with the concepts introduced in Part 7 — Phase2 Dual Write. Review it first if the terminology in this part is unfamiliar. 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: Phase 3 cutover executes an immediate 100% traffic shift for stable read services and a graduated ramp over 10 days for transactional services. Legacy Magento remains a hot standby for 30 days while automated ArgoCD gitops pipelines handle production deployments. ...

Prerequisite: Familiarity with the concepts introduced in Part 9 — Outbox Saga. Review it first if the terminology in this part is unfamiliar. Answer-first: Architectural Decision Records (ADRs) enforce three core principles: resilience over simplicity, strict layer standardization, and explicit event-driven boundaries. Standardizing service layouts, outbox patterns, and database migrations before writing code ensures consistent microservices governance across large engineering teams. 21 services. 24 decisions. 3.5 months of deliberation captured in Architecture Decision Records. ...

GitOps at Scale: Kubernetes & ArgoCD for Microservices Building 21 well-architected Go microservices is only half the battle. If your deployment process relies on an engineer running kubectl apply from their laptop on a Friday afternoon, you haven’t built an enterprise platform — you’ve built a ticking time bomb. When designing this composable e-commerce ecosystem, we made one hard architectural rule from day one: no human touches the production cluster directly. Everything flows through Git. ArgoCD enforces it. Choosing EKS over ECS was a key architectural decision that enabled this first-class GitOps model; for a full cost and scaling breakdown, see our AWS EKS vs ECS Comparison. ...