Canary Release

Overview 2 AM. A ride-hailing platform’s payment service does a blue-green switch. The on-call engineer runs kubectl rollout to flip the Service selector, shifting traffic from blue to green. Everything looks fine — Pods are Ready, health checks pass, response latency looks normal. Three minutes later, the DBA chat explodes. Database connections spike from 200 to 1,200, the connection pool is maxed out, and five downstream services all time out. Root cause: the green environment’s app version updated the ORM framework, and the default pool size jumped from 20 to 100....

Overview Migrating 120+ microservices from traditional VM deployments to Kubernetes sounds like a standard project: write Dockerfiles, build a cluster, migrate services, shift traffic. In planning meetings, everyone thinks three months is enough. In practice, you discover that the real challenges aren’t about “how to get services running” — that’s just helm install — but about pitfalls nobody warned you about: circular dependencies in service graphs, in-memory state loss during stateful migration, CNI performance cliffs at scale, DNS caching traps during canary traffic shifts, ConfigMap bloat, and monitoring metric gaps after migration....