1. Docker Image Best Practices

• Use Official Base Images: Start from slim, maintained images (e.g., node:18-alpine, python:3.11-slim) to reduce attack surface.
• Minimize Layers: Combine related RUN commands and clean up caches to keep images small:

  RUN apt-get update &&     apt-get install -y build-essential &&     rm -rf /var/lib/apt/lists/*

• Leverage Multi-Stage Builds: Separate your build and runtime environments:

  FROM golang:1.20-alpine AS builder
  WORKDIR /app
  COPY . .
  RUN go build -o app
  
  FROM alpine:latest
  COPY --from=builder /app/app /usr/local/bin/app
  ENTRYPOINT ["/usr/local/bin/app"]

• Pin Dependencies: Use explicit versions in package.json or go.mod to ensure reproducible builds.
• Avoid Running as Root: Create an unprivileged user for your application:

  RUN addgroup -S appgroup && adduser -S appuser -G appgroup
  USER appuser

2. Kubernetes Architecture & Design

• Namespace Segmentation: Use namespaces to isolate environments (e.g., dev, staging, prod).
• Resource Requests & Limits: Define CPU/memory requests and limits to avoid noisy neighbors:

  resources:
    requests:
      cpu: "100m"
      memory: "128Mi"
    limits:
      cpu: "500m"
      memory: "512Mi"

• Use Deployments & StatefulSets Appropriately: - Deployment for stateless services. - StatefulSet for stateful workloads requiring stable network IDs and storage.
• ConfigMaps & Secrets: Manage configuration outside containers and store sensitive data securely.
• Probes for Health Checks: Configure livenessProbe and readinessProbe to ensure pod health:

  livenessProbe:
    httpGet:
      path: /health
      port: 8080
    initialDelaySeconds: 30
    periodSeconds: 10

3. CI/CD Integration

1. Automate Builds & Tests: Trigger Docker image builds and unit/integration tests on every commit.
2. Push to Registry: Use a registry like Docker Hub, ECR, or GCR. Tag images with git SHA or semantic versions.
3. Deploy with GitOps: Tools like Argo CD or Flux can sync Kubernetes manifests from Git repositories automatically.
4. Canary & Blue/Green Deployments: Reduce risk by gradually rolling out changes and enabling quick rollbacks.

4. Monitoring & Logging

• Centralized Logging: Aggregate logs with tools like Elasticsearch / Fluentd / Kibana (EFK) or Loki / Promtail / Grafana.
• Metrics & Alerts: Use Prometheus + Grafana for metrics collection and alerting on CPU, memory, and custom application metrics.
• Distributed Tracing: Implement tracing (Jaeger, Zipkin) to troubleshoot performance bottlenecks across microservices.

5. Security Considerations

• Image Scanning: Scan images for vulnerabilities using tools like Trivy or Clair during your CI pipeline.
• Pod Security Policies / OPA Gatekeeper: Enforce policies on pod specs, e.g., non-root users and allowed volumes.
• Network Policies: Restrict pod-to-pod traffic with Kubernetes NetworkPolicies.
• RBAC: Implement fine-grained Role-Based Access Control to limit privileges.