Kubernetes Patterns — Structural & Configuration Patterns

The third Kubernetes Patterns episode combines structural and configuration patterns. The panel stresses that every book pattern must fit the actual platform. An Init Container prepares data or configuration before the application starts; it should be idempotent, have explicit resources, and finish predictably.

A Sidecar adds file refresh, proxying, or telemetry to a pod, but also resource, versioning, and operational costs. With platform control, shared behavior may be better delivered as a library or injected transparently. An Adapter normalizes an interface, while an Ambassador isolates network protocols and remote access.

Configuration is separated from the image: environment variables fit simple values, files and ConfigMaps add structure, and the application decides whether to accept updates without restarting. Secrets need access controls and encryption because base64 is not protection. Immutable Configuration binds settings to a rollout.

A Configuration Template assembles the final file from environment parameters in a separate container, but increases diagnostic and security complexity. More overlapping sources and templates make effective state harder to understand. Composition works when responsibilities are visible and configuration remains versioned and testable.