Kubernetes for Developers: A Practical Guide from Docker to K8s

Kubernetes isn't just for Ops teams. Learn the essentials of container orchestration to deploy, scale, and manage your applications with confidence.

📅 November 24, 2025•⏱️ 30 min read•🏷️ DevOps

Introduction

"It works on my machine" is a phrase every developer dreads. Docker solved this by packaging apps into containers. But what happens when you have hundreds of containers? How do you manage them, scale them, and ensure they are always running?

That's where Kubernetes (K8s) comes in. It's the operating system for the cloud. In 2025, understanding K8s primitives is as essential as knowing Git.

💡 Why This Matters: K8s gives you the power to define your infrastructure as code, ensuring your production environment matches your design perfectly.

Before K8s: Docker

Everything in K8s starts with a container image. Here is a standard Dockerfile for a Spring Boot application.

Dockerfile

FROM eclipse-temurin:17-jdk-alpine AS build
WORKDIR /workspace/app

COPY mvnw .
COPY .mvn .mvn
COPY pom.xml .
COPY src src

RUN ./mvnw install -DskipTests
RUN mkdir -p target/dependency && (cd target/dependency; jar -xf ../*.jar)

FROM eclipse-temurin:17-jre-alpine
VOLUME /tmp
ARG DEPENDENCY=/workspace/app/target/dependency
COPY --from=build ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY --from=build ${DEPENDENCY}/META-INF /app/META-INF
COPY --from=build ${DEPENDENCY}/BOOT-INF/classes /app
ENTRYPOINT ["java","-cp","app:app/lib/*","com.example.DemoApplication"]

Core Concepts

Deployment Manifest

This YAML file tells Kubernetes how to run your Spring Boot application. It defines the number of replicas, resource limits, and environment variables.

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-boot-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: spring-boot-app
  template:
    metadata:
      labels:
        app: spring-boot-app
    spec:
      containers:
      - name: spring-boot-app
        image: my-registry/spring-boot-app:v1
        ports:
        - containerPort: 8080
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        env:
        - name: SPRING_PROFILES_ACTIVE
          value: "prod"
        livenessProbe:
          httpGet:
            path: /actuator/health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10

Security Considerations

Kubernetes is secure by design, but configuration matters.

🔒 RBAC

Use Role-Based Access Control to limit who can do what in the cluster.

🔒 Secrets

Never store passwords in plain text. Use K8s Secrets or Vault.

🔒 Network Policies

Restrict traffic between Pods. Only allow necessary communication.

🔒 Image Scanning

Scan Docker images for vulnerabilities before deployment.

✅ Deployment Checklist

Ready to push to prod?

Validate Your Config

Use our tools to validate JSON and YAML configurations before applying them.

Explore Tools →Read More Blogs

Conclusion

Kubernetes is a steep learning curve, but the payoff is immense. It provides a standard language for deploying and managing software anywhere—on-prem, AWS, Google Cloud, or Azure.

By mastering Docker and the basic K8s objects (Pods, Deployments, Services), you unlock the ability to build truly cloud-native, resilient applications.