Series: 30 Days DevOps Interview Preparation
Author: Tathagat Gaikwad

Welcome to Day 27 of my 30-Day DevOps + Cloud + SRE Interview Preparation Challenge.
Today’s focus is on Kubernetes (K8s) – the de facto standard for container orchestration.

If you’ve ever wondered:
👉 How do big companies like Netflix, Spotify, and Amazon deploy and scale thousands of containers daily?
👉 How do we ensure applications stay up even if servers fail?

The answer is: Kubernetes.

🔹 What is Kubernetes?

Kubernetes (often abbreviated as K8s) is an open-source container orchestration platform originally developed by Google.

It automates:

📦 Container deployment
📈 Scaling applications up or down
⚖️ Load balancing traffic
💀 Self-healing (restarting failed containers, rescheduling them on healthy nodes)
🔄 Rolling updates and rollbacks

👉 Think of Docker as a shipping container and Kubernetes as the global logistics company managing thousands of containers across the globe.

🏗️ Core Kubernetes Concepts

Pod → The smallest deployable unit in Kubernetes. A Pod usually runs one container, but can run multiple tightly coupled containers.
Deployment → Ensures that the right number of Pods are running. Provides rolling updates and rollbacks.
ReplicaSet → Maintains a stable set of replicas (Pods).
Service → Exposes Pods to the network.
- ClusterIP → Internal access only within the cluster.
- NodePort → Exposes the service externally via NodeIP:Port.
- LoadBalancer → Integrates with cloud providers (AWS, GCP, Azure) to expose services externally with load balancing.

🛠️ Practical – Setting up Kubernetes on AWS EKS

For today’s hands-on, we’ll use Amazon Elastic Kubernetes Service (EKS) – a managed Kubernetes service.

Step 1: Install Prerequisites

# Install AWS CLI
sudo apt-get update && sudo apt-get install -y awscli  

# Install eksctl (EKS cluster creation tool)
curl --location "https://github.com/weaveworks/eksctl/releases/latest/download/eksctl_$(uname -s)_amd64.tar.gz" | tar xz
sudo mv eksctl /usr/local/bin  

# Install kubectl
curl -o kubectl https://amazon-eks.s3.us-west-2.amazonaws.com/latest/bin/linux/amd64/kubectl
chmod +x ./kubectl
sudo mv ./kubectl /usr/local/bin

Step 2: Create an EKS Cluster

eksctl create cluster \
--name devops-cluster \
--version 1.28 \
--region ap-south-1 \
--nodegroup-name devops-nodes \
--node-type t3.medium \
--nodes 2 \
--nodes-min 1 \
--nodes-max 3 \
--managed

This creates:

A Kubernetes cluster named devops-cluster
2 worker nodes in AWS

Step 3: Verify Cluster Connection

kubectl get nodes
kubectl cluster-info

You should see your EKS nodes ready. 🎉

Step 4: Deploy a Sample App

# Create a deployment
kubectl create deployment myapp --image=nginx  

# Expose it as a NodePort service
kubectl expose deployment myapp --type=NodePort --port=80  

# Get the service details
kubectl get svc myapp

Now, access your app at http://<NodePublicIP>:<NodePort>.

Step 5: Scale and Rollout

# Scale to 3 replicas
kubectl scale deployment myapp --replicas=3  

# Check rollout status
kubectl rollout status deployment/myapp  

# Update image (rolling update)
kubectl set image deployment/myapp nginx=nginx:1.21 --record  

# Rollback if needed
kubectl rollout undo deployment/myapp

🎯 Kubernetes Interview Questions & Detailed Answers

Q1: What is the difference between Docker and Kubernetes?
👉 Docker is for building and running containers.
👉 Kubernetes is for managing containers across multiple hosts (scheduling, scaling, networking).
They complement each other, not replace.

Q2: What is a Pod in Kubernetes?
👉 A Pod is the smallest unit in Kubernetes, representing a running process.

Usually holds 1 container
Can hold multiple tightly coupled containers (e.g., a main app + sidecar container)
All containers inside a Pod share the same IP address, network, and storage.

Q3: How does Kubernetes ensure high availability?
👉 Kubernetes ensures HA by:

Maintaining the desired state via Deployments and ReplicaSets.
Rescheduling Pods to healthy nodes if a node crashes.
Distributing traffic via Services and Load Balancers.

Q4: What is the difference between ClusterIP, NodePort, and LoadBalancer?

ClusterIP → Default, internal-only, used for communication inside the cluster.
NodePort → Exposes app externally on a specific port across all nodes (<NodeIP>:<Port>).
LoadBalancer → Integrates with cloud providers to automatically create an external load balancer.

Q5: How do rolling updates and rollbacks work in Kubernetes?

Rolling Update: Replaces Pods gradually without downtime.

kubectl set image deployment/myapp nginx=nginx:1.21 --record

Rollback: Reverts to the previous working version.

kubectl rollout undo deployment/myapp

✅ Takeaways from Day 27

Kubernetes is the industry standard for container orchestration.
Hands-on practice with Pods, Deployments, and Services gives you confidence for interviews.
Cloud-native DevOps roles almost always expect basic Kubernetes knowledge.

💡 If you’re also preparing for DevOps interviews, let’s connect!
I’ll share more daily learnings + projects in this #30DaysOfDevOps journey.

#DevOps #Kubernetes #AWS #EKS #Cloud #SRE #InterviewPreparation

🚀 Day 27/30 – Kubernetes Basics with AWS EKS | 30 Days DevOps + Cloud + SRE Interview Prep