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Aisalkyn Aidarova
Aisalkyn Aidarova

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interview questions and answers

If you're interviewing for a Senior DevOps Engineer (5–7 years), you should not only know definitions. You should understand why the technology exists, what problem it solves, how it works internally, and when to use it.

1. What is AWS?

Interview Question

What is AWS?

Answer

AWS (Amazon Web Services) is a cloud computing platform provided by Amazon Web Services.

Instead of buying physical servers, networking equipment, and storage, companies rent resources from AWS on demand.

AWS provides:

  • Compute (EC2, Lambda, ECS, EKS)
  • Storage (S3, EBS, EFS)
  • Networking (VPC, Route53, ELB)
  • Databases (RDS, DynamoDB)
  • Security (IAM, KMS, Secrets Manager)

Why Companies Use AWS

Traditional Infrastructure:

Buy Server
Install OS
Configure Network
Manage Hardware
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AWS:

Create EC2
Deploy Application
Done
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Benefits:

  • No hardware management
  • High availability
  • Pay as you go
  • Auto scaling
  • Global presence

2. What is an Operating System?

Interview Question

What is an Operating System?

Answer

An Operating System (OS) is software that sits between hardware and applications.

Without an OS:

Application
    ↓
Hardware
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Application would need to control:

  • CPU
  • Memory
  • Disk
  • Network Card

directly.

With OS:

Application
      ↓
Operating System
      ↓
Hardware
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Examples:

  • Linux
  • Windows
  • macOS

3. Linux Architecture

Interview Question

Explain Linux Architecture.

Answer 

User
 ↓
Shell
 ↓
Kernel
 ↓
Hardware
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Shell

Interface where users type commands.

Examples:

ls
pwd
cd
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Popular shells:

  • Bash
  • Zsh
  • Sh

Kernel

Brain of Linux.

Responsibilities:

  • CPU scheduling
  • Memory management
  • Process management
  • Device communication

Hardware

Physical components:

  • CPU
  • RAM
  • SSD
  • Network Card

4. Hardware Components

Interview Question

Explain major hardware components.

CPU

Brain of computer.

Responsible for:

  • Executing instructions
  • Running applications

Check CPU:

lscpu
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RAM

Temporary memory.

Stores:

  • Running processes
  • Application data

Check RAM:

free -h
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SSD

Permanent storage.

Stores:

  • OS
  • Files
  • Applications

Check disk:

df -h
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Network Interface Card (NIC)

Responsible for network communication.

Check:

ip addr
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5. Linux Process Management

Interview Question

What is a Process?

Answer

A process is a running program.

Examples:

nginx
java
python
docker
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View processes:

ps -ef
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or

top
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6. Systemd

Interview Question

What is systemd?

Answer

Systemd is Linux's service manager.

Used to:

  • Start services
  • Stop services
  • Restart services
  • Manage boot process

Examples:

systemctl start nginx
systemctl stop nginx
systemctl restart nginx
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Check status:

systemctl status nginx
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7. Journalctl

Interview Question

How do you check service logs?

Answer 

journalctl -u nginx
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Last 100 lines:

journalctl -u nginx -n 100
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Live logs:

journalctl -f
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8. Network Troubleshooting

Interview Question

User cannot access website. How do you troubleshoot?

Step 1: Verify DNS 

nslookup google.com
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or

dig google.com
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Step 2: Verify Network 

ping google.com
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Step 3: Verify Route 

traceroute google.com
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Step 4: Verify Port 

telnet website.com 443
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or

nc -zv website.com 443
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Step 5: Verify Listening Port 

ss -tulnp
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or

netstat -tulnp
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Step 6: Check Firewall 

iptables -L
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or

ufw status
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9. EC2

Interview Question

What is EC2?

Answer

Amazon EC2 is a virtual machine running inside AWS.

You choose:

  • CPU
  • RAM
  • Disk
  • OS

AWS creates server for you.

Example:

Ubuntu
4 vCPU
16GB RAM
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10. EBS

Interview Question

What is EBS?

Answer

Amazon EBS is block storage attached to EC2.

Think:

EC2 = Computer
EBS = Hard Drive
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Characteristics:

  • Persistent
  • Attached to one instance
  • Fast
  • Supports snapshots

Example:

EC2
 └── EBS Volume (100GB)
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11. EFS

Interview Question

What is EFS?

Answer

Amazon EFS is a shared file system.

Multiple EC2 servers can mount same storage.

EC2-1
EC2-2
EC2-3
   ↓
EFS
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Uses NFS protocol on:

Port 2049
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EBS vs EFS

Feature EBS EFS
Shared No Yes
Multiple Servers No Yes
Protocol Block NFS
Use Case Database Shared Files

12. S3

Interview Question

What is S3?

Answer

Amazon S3 is object storage.

Stores:

  • Images
  • Videos
  • Backups
  • Logs

Structure:

Bucket
 ├── image.png
 ├── file.pdf
 └── backup.zip
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Characteristics:

  • Unlimited storage
  • 11 nines durability
  • Cheap

Common Use Cases

  • Log storage
  • Static websites
  • Backup storage
  • Data lake

13. Lambda

Interview Question

What is Lambda?

Answer

AWS Lambda runs code without managing servers.

Traditional:

EC2
Install OS
Patch Server
Run Code
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Lambda:

Upload Code
Execute Function
Done
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Triggers:

  • API Gateway
  • S3 Upload
  • EventBridge
  • SNS

Example

User uploads file:

S3 Upload
   ↓
Lambda Trigger
   ↓
Resize Image
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14. API Gateway

Interview Question

What is API Gateway?

Answer

Amazon API Gateway is a front door for APIs.

Flow:

User
 ↓
API Gateway
 ↓
Lambda
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Responsibilities:

  • Authentication
  • Authorization
  • Rate limiting
  • Routing

Example 

GET /students
POST /students
DELETE /students
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API Gateway routes requests.

15. Application Load Balancer (ALB)

Interview Question

What is ALB?

Answer

Application Load Balancer distributes traffic across multiple servers.

Without ALB:

10000 users
      ↓
Single Server
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Server crashes.

With ALB:

10000 users
      ↓
ALB
   ↓    ↓
EC2-1 EC2-2
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Traffic distributed.

Layer

Works at:

OSI Layer 7
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HTTP/HTTPS.

Supports

  • Path routing
  • Host routing
  • SSL termination

Example:

/api → Backend
/images → Frontend
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16. Auto Scaling Group (ASG)

Interview Question

What is ASG?

Answer

Amazon EC2 Auto Scaling automatically adds or removes EC2 instances.

Example:

Normal:

2 EC2
CPU 30%
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Traffic spike:

CPU 90%
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ASG launches:

4 EC2
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Traffic drops:

Back to 2 EC2
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ASG + ALB Together

Production architecture:

Users
   ↓
ALB
   ↓
Target Group
   ↓
Auto Scaling Group
   ↓
EC2 Instances
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ALB distributes traffic.

ASG maintains healthy servers.

17. Senior DevOps Scenario Question

Interview Question

A website is down. How do you troubleshoot?

Answer

  1. Check DNS 
nslookup website.com
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  1. Check connectivity 
ping website.com
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  1. Check load balancer health
  • ALB Target Group
  1. Check EC2 
systemctl status nginx
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  1. Check logs 
journalctl -u nginx
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  1. Check disk 
df -h
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  1. Check memory 
free -h
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  1. Check CPU 
top
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  1. Check listening ports 
ss -tulnp
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  1. Check security groups and NACLs.

This step-by-step troubleshooting approach is what interviewers expect from a DevOps engineer with several years of experience.

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