Kubernetes

Kubernetes (K8s)

Kubernetes is the standard for orchestrating containerized applications. In 2025, the Gateway API has replaced Ingress as the standard for traffic routing, and Sidecars are native.

When to Use

• Scale: You have hundreds of microservices.
• Resilience: You need self-healing, auto-restart, and multi-zone availability.
• Platform Building: You are building an internal platform (IDP) for developers.

Quick Start (Gateway API)

# Gateway (The Load Balancer)
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: my-gateway
spec:
  gatewayClassName: nginx
  listeners:
    - name: http
      protocol: HTTP
      port: 80

---
# HTTPRoute (The Routing Rule)
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: my-app
spec:
  parentRefs:
    - name: my-gateway
  rules:
    - matches:
        - path:
            type: PathPrefix
            value: /api
      backendRefs:
        - name: my-service
          port: 8080

Core Concepts

Control Plane

API Server, etcd, Scheduler. The brain of the cluster.

Gateway API

The successor to Ingress. Split roles between Infrastructure Provider (GatewayClass), Cluster Operator (Gateway), and Developer (HTTPRoute/GRPCRoute).

Custom Resource Definitions (CRDs)

Extend K8s API. Used by Operators (e.g., Prometheus Operator, Postgres Operator) to manage complex stateful apps.

Best Practices (2025)

Do:

• Use Gateway API: Stop writing new Ingress resources.
• Use GitOps: ArgoCD or Flux to manage cluster state.
• Set Requests/Limits: The scheduler needs them to bin-pack nodes efficiently.
• Use Native Sidecars: K8s 1.29+ supports restartPolicy: Always for init containers, making sidecars first-class.

Don't:

• Don't use latest tag: Always pin image versions (SHA or specific tag) for reproducibility.

References

• Kubernetes Documentation

Source: G1Joshi/Agent-Skills — distributed by TomeVault.