Docker Swarm vs Kubernetes: Lessons from a Production Migration
Starting with Simple Docker Deployments
Simple Docker deployments were effective while the platform had a small number of services and predictable traffic. As the system grew, deployment coordination, recovery, configuration, and persistent storage required more structured orchestration.
ReplicaSets
ReplicaSets introduced a declared number of application instances and automatic replacement when a container failed. This made availability an expected system state rather than a manual recovery task.
Services
Kubernetes Services provided stable internal networking even while pods were replaced or rescheduled. Applications could communicate through service names instead of tracking changing container addresses.
Ingress
Ingress rules centralized external HTTP routing, TLS termination, and host or path-based routing instead of configuring those concerns independently for every container.
ConfigMaps and Secrets
ConfigMaps separated environment configuration from container images, while Secrets provided a controlled mechanism for credentials and other sensitive settings. This allowed the same image to move safely between environments.
Persistent Volumes
Persistent Volumes separated application lifecycle from storage lifecycle. Stateful workloads could retain data even when pods were recreated or moved between nodes.
When Kubernetes Was Worth It
Kubernetes added operational complexity, so the migration was justified by scale and reliability requirements rather than technology preference. Its value became clear when the platform needed repeatable rollouts, self-healing workloads, stable discovery, centralized configuration, and portable infrastructure conventions.