DEVOPS INTERVIEW QUESTION

 AWS, Docker, Kubernetes & DevOps Concepts Explained with Easy Tricks

1. What Is a Route Table & How Does Traffic Flow?

A Route Table in AWS is like a GPS for your Virtual Private Cloud (VPC). It controls the direction of both internal and external network traffic within your AWS environment.

🔍 How It Works:

• A request originates from a resource (like an EC2 instance).

• AWS checks the route table for a rule that matches the destination IP.

• If a rule is found, the request is routed accordingly (e.g., to an Internet Gateway, NAT Gateway, or local target).

• If no matching rule is found, the traffic is discarded.

🧠 Memory Trick: “Route Table is like Google Maps for your AWS network.”

2. Internet Gateway vs NAT Gateway

These gateways help your AWS instances connect to the internet, but in different ways.

• Internet Gateway (IGW): Enables both inbound and outbound internet access for instances in public subnets.

• NAT Gateway: Allows only outbound internet access from private subnets. It blocks incoming traffic to keep internal instances secure.

📌 Example:

Use IGW for your web server and NAT for backend servers needing internet access for updates.

🧠 Memory Trick: “IGW = Two-way street. NAT = One-way OUT.”

3. Default Protocol in AWS Route Table

By default, AWS Route Tables operate using IPv4. While IPv6 is supported, it's primarily used for specialized configurations or compliance needs.

🧠 Memory Trick: “IPv4 is your AWS instance’s postal address.”

4. Disaster Recovery (DR) in AWS

Disaster Recovery ensures business continuity when your primary systems fail. AWS offers 4 strategies:

• Backup & Restore: Regular backups stored in S3 or Glacier.

• Pilot Light: Keep a minimal copy of the system always running.

• Warm Standby: A scaled-down version runs continuously.

• Multi-site (Active-Active): Fully functional duplicate environment in another region.

🧠 Memory Trick: “BPWM – Backup Power With Minimum downtime!”

5. High Availability (HA) vs Disaster Recovery (DR)

• High Availability (HA): Keeps your services running with minimal downtime using redundancy (multiple instances, AZs).

• Disaster Recovery (DR): Focuses on restoring operations after an unexpected failure.

📌 Example:

An e-commerce site may use HA to stay live 24/7 and DR to recover from region-wide failures.

🧠 Memory Trick: “HA = No downtime. DR = Quick recovery!”

6. Snapshot vs Image (AMI) in AWS

• Snapshot: A backup of a specific volume (e.g., EBS volume) at a given point in time. It does not include instance configuration.

• AMI (Amazon Machine Image): A complete image including OS, data, and configurations needed to launch a fully working EC2 instance.

🧠 Memory Trick: “Snapshot = Partial. Image = Full system clone.”

7. Connecting to Private EC2 Without a Private Key

Lost your private key? Here are alternatives:

• Use EC2 Instance Connect (for supported AMIs like Amazon Linux 2).

• Create a new key pair, and use another instance in the same subnet to update the authorized_keys file.

• Use SSM Session Manager (if previously configured with the right IAM role and agent).

🧠 Memory Trick: “EC2 Connect = Emergency door when key is lost.”

8. Types of Networks in Docker

Docker supports several networking options:

• Bridge (default): Isolated network for container communication.

• Host: Shares the host’s networking stack.

• Overlay: Enables multi-host networking in Docker Swarm.

• Macvlan: Assigns MAC address to containers for direct LAN communication.

• None: Disables networking for containers.

🧠 Memory Trick: “BHOMN – Be Happy On My Network!”

9. CMD vs ENTRYPOINT in Docker

• CMD: Defines default behavior, but can be overridden by arguments passed during docker run.

• ENTRYPOINT: Specifies a fixed command that always runs, and accepts additional arguments via CMD.

📌 Tip:

Use ENTRYPOINT for mandatory tasks and CMD for optional configuration.

🧠 Memory Trick: “CMD = Flexible. ENTRYPOINT = Fixed.”

10. Docker Architecture

Docker follows a client-server architecture:

• Client: Accepts user commands.

• Daemon: Runs in the background, manages containers and images.

• Registry: Stores Docker images (e.g., Docker Hub, ECR).

🧠 Memory Trick: “Client asks, Daemon does, Registry stores.”

11. Jenkins Prerequisites

Before installing Jenkins, ensure:

• Java is installed (Jenkins runs on Java).

• Git is available to clone repositories.

• A server or cloud VM is ready to host Jenkins.

Bonus tools: Maven, Gradle, or Docker for advanced builds.

🧠 Memory Trick: “JGS = Java, Git, Server – Jenkins needs all three.”

12. Git Clone vs Git Fork

• Clone: Copies a repository from GitHub to your local machine.

• Fork: Copies the repo to your own GitHub account so you can make independent changes.

🧠 Memory Trick: “Fork to own, Clone to use.”

13. Maximum VPCs in AWS

By default, AWS allows 5 VPCs per region. You can request more through a Service Quota Increase.

🎓 Tip:

This is a frequent question in AWS certifications.

14. Transit Gateway vs VPC Peering

• VPC Peering: Direct, one-to-one connection between two VPCs.

• Transit Gateway: Acts as a central hub to connect multiple VPCs or on-premises networks.

🧠 Memory Trick: “Peering = Two-way road. Transit = Highway connection.”

15. What is Runtime?

A Runtime is the execution environment for code. It includes the language engine, libraries, and dependencies.

🧪 Examples:

• Java: JVM

• Python: Python Interpreter

• JavaScript: Node.js

🧠 Memory Trick: “Runtime is the kitchen where your code is cooked!”

16. Load Balancer in Kubernetes

In Kubernetes, the LoadBalancer service type creates an external IP to distribute traffic across Pods in a deployment.

🛣️ Why it’s important:

It ensures high availability and even load distribution to prevent failure due to overload.

🧠 Memory Trick: “LoadBalancer = Traffic cop for your pods.”

17. Default Network in Docker

When you create a Docker container without specifying a network, it joins the bridge network by default. This allows containers to communicate securely.

🧠 Memory Trick: “Bridge helps connect containers together.”

18. Default Folder Permission in Linux

Linux default folder permission is typically 755:

• Owner (7): Read, write, execute.

• Group (5): Read, execute.

• Others (5): Read, execute.

Use ls -l to inspect permissions.

🧠 Memory Trick: “7 for owner, 5 for group, 5 for others.”

19. Kubernetes Node Architecture

• Master Node: Manages cluster state, scheduling, and overall orchestration.

• Worker Nodes: Run the actual containers (Pods) using components like kubelet, kube-proxy.

Master includes:

• etcd

• kube-apiserver

• kube-scheduler

• kube-controller-manager

🧠 Memory Trick: “Master commands. Workers obey.”

20. Why is Replication Needed?

Replication ensures high availability, fault tolerance, and scalability of services.

Benefits:

• Minimizes downtime.

• Handles more user traffic by sharing the load.

• Provides data redundancy.

🧠 Memory Trick: “Replication = Photocopy your data just in case!”

✨ Final Thoughts

Whether you're preparing for a DevOps interview or simply strengthening your cloud concepts, these 20 core ideas and memory tricks can make your learning journey easier and faster.

📌 Bookmark this article and revisit it before any interview or certification. It could be your cheat sheet to cracking the next big opportunity!

Conclusion

AWS, Docker, and Kubernetes are essential technologies for cloud and DevOps engineers. Understanding these concepts and using tricks to remember them makes learning easier. Keep practicing and implementing these technologies to build expertise!

By mastering these topics, you can confidently handle cloud architecture, containerization, and automation tasks efficiently.

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