Kubernetes Deployments vs. Argo Rollouts: How Traffic Really Switches Between Old and New Versions When I first started learning Kubernetes deployments, I understood the concepts of Rolling Update , Blue-Green , and Canary . But one question kept bothering me: How does Kubernetes actually switch users from the old version to the new version? Does it change the Service? Does it move traffic? Does it kill old pods first? After digging into Kubernetes and Argo Rollouts, I realized that understanding ReplicaSets, Services, and readiness probes makes everything much easier. Let's walk through it step by step. Standard Kubernetes Deployment A normal Kubernetes deployment uses a Deployment resource.  kind: Deployment The Deployment controller is responsible for updating your application. Suppose your application is currently running Version 1. Users │ Kubernetes Service │ ReplicaSet (Version 1) ├── ...