Platform Engineer: Interview Questions(Basics)

Platform Engineering: Core Concepts Explained

Platform Engineer: Interview Questions & Answers

Platform Engineer: Interview Questions(Basics)

Platform Engineer: Interview Questions(Coding)

Platform Engineer: Practical Design Problems

Platform Engineer: Interview Questions(Advanced)

Linux Fundamentals

1. What happens internally when you run a command like `ls` in a shell?

Answer:

The shell parses the command and calls fork() to create a child process.

The child calls exec() to replace its memory with /bin/ls.

The kernel handles file access via syscalls (e.g. open(), readdir(), write()).

Output is written to stdout (file descriptor 1).

// Underlying C system calls
fork();
execvp("ls", args);

Scorecard:

5 – Mentions fork/exec, syscalls, file descriptors
3 – Describes at a high level (command, output)
1 – Can’t explain or confuses core parts

For: Junior, Senior

2. How do `fork` and `exec` work in Linux, and why are they important?

Answer:

fork() creates a duplicate process.

exec() replaces the child’s memory space with a new program.

This is how Linux spawns new processes without loading a full new shell.

pid_t pid = fork();
if (pid == 0) execvp(cmd, args);  // child

Scorecard:

5 – Explains fork/exec separation and process model clearly
3 – Describes behavior but not relationship
1 – Confuses their roles or thinks they’re the same

For: Junior, Senior

3. What's the difference between a process and a thread?

Answer:

A process has its own memory space and system resources.

A thread shares the memory and resources of the parent process.

Threads are lightweight and faster to spawn but require synchronization.

# View threads of a process
ps -T -p <PID>

Scorecard:

5 – Clearly distinguishes memory/resource sharing and gives examples
3 – Understands difference but lacks depth
1 – Confuses or interchanges the two

For: Junior, Senior

4. How can you find which process is using a specific port?

Answer:

Use tools like lsof, netstat, or ss.

lsof -i :8080
netstat -tulnp | grep 8080
ss -ltnp | grep 8080

These commands show the PID and process name.

Scorecard:

5 – Knows multiple tools and explains output
3 – Uses one command correctly
1 – Doesn’t know or guesses incorrectly

For: Junior, Senior

5. Explain what a zombie process is and how to clean it up.

Answer:

A zombie is a completed child process not reaped by its parent.

It stays in the process table with a status Z.

You can clean it by killing the parent or ensuring it calls wait().

ps aux | grep Z

Scorecard:

5 – Understands the parent-child relationship and wait()
3 – Defines zombie but not cleanup
1 – Thinks it’s an active or harmful process

For: Junior, Senior

6. How does Linux handle memory allocation (RSS vs Virtual Memory)?

Answer:

RSS (Resident Set Size): Actual physical memory used.

Virtual Memory: Total memory the process can access (may include swapped or unmapped pages).

cat /proc/<pid>/status

Scorecard:

5 – Correctly explains both and uses tools like /proc or smem
3 – Vaguely aware of virtual memory
1 – Confuses the two or guesses

For: Junior, Senior

7. What are inodes and how do they relate to files?

Answer:

An inode stores metadata about a file (owner, permissions, timestamps, etc.).

The filename is just a pointer to an inode.

ls -i file.txt
stat file.txt

Scorecard:

5 – Explains metadata concept and separation from filename
3 – Understands inode basics
1 – Thinks inode is part of filename or doesn’t know

For: Junior, Senior

8. What’s the difference between a hard link and a symbolic link?

Answer:

A hard link points directly to the same inode.

A symlink points to the file path and can break if the target is removed.

ln original.txt hardlink.txt
ln -s original.txt symlink.txt

Scorecard:

5 – Correctly explains and shows both use cases
3 – Understands one type
1 – Thinks they're the same

For: Junior, Senior

9. How would you check disk I/O performance?

Answer:

Use iostat, iotop, or dstat.

iostat -dx 1
iotop
dstat -cdngy

Look for high await, util, or heavy I/O processes.

Scorecard:

5 – Uses appropriate tools and knows metrics
3 – Names tools but not interpretation
1 – No clue or uses wrong tools (e.g. top only)

For: Junior, Senior

10. What happens if you delete a file that is still open by a process?

Answer:

The file is removed from the directory listing, but the data remains on disk until all file descriptors are closed.

lsof | grep deleted

Scorecard:

5 – Explains descriptor-handle concept and cleanup
3 – Partial understanding
1 – Thinks file is immediately wiped

For: Junior, Senior

11. How do file permissions work in Linux? (`chmod`, `chown`, etc.)

Answer:

Permissions: r (4), w (2), x (1) — for owner, group, others

chmod 750 script.sh
chown user:group file
ls -l file

Scorecard:

5 – Explains bits, uses examples, understands chown and chmod
3 – Knows how to use commands
1 – No clue or misuses commands

For: Junior, Senior

12. How does the `fstab` file work and when is it used?

Answer:

/etc/fstab defines filesystems to mount at boot.

Each line contains device, mount point, type, and options.

/dev/sda1 / ext4 defaults 0 1
mount -a  # to test

Scorecard:

5 – Explains format, knows testing and troubleshooting
3 – Knows it's for auto-mounting
1 – Never used it or confuses with mount

For: Junior, Senior

13. What does the `fstat()` syscall do and how is it different from `stat()`?

Answer:

stat() works with file paths.
fstat() works with file descriptors.

struct stat s;
fstat(fd, &s);  // open file

Scorecard:

5 – Understands syscall-level detail
3 – Vaguely explains usage
1 – Doesn’t know or mixes up terms

For: Senior

14. How do you check open files on a system or per-process?

Answer:

lsof              # all open files
lsof -p <PID>     # per-process
ls /proc/<pid>/fd

Useful for file descriptor leaks or log cleanup.

Scorecard:

5 – Uses multiple tools with correct context
3 – Knows lsof
1 – Doesn’t know any method

For: Junior, Senior

15. How do you monitor real-time file system usage (space and inodes)?

Answer:

df -h     # disk usage
df -i     # inode usage
du -sh *  # per-directory usage

Check for inode exhaustion on systems with lots of small files.

Scorecard:

5 – Differentiates inode vs block usage
3 – Knows df but not -i
1 – Uses wrong tools or guesses

For: Junior, Senior

Networking

1. What is the difference between TCP and UDP?

Answer:

TCP is connection-oriented, reliable, with built-in error handling and retransmission.
UDP is connectionless, faster, but does not guarantee delivery or order.

Used cases:

TCP: web, SSH, email
UDP: DNS, video streaming, games

# Check listening TCP and UDP ports
ss -tuln

Scorecard:

5 – Explains reliability, ordering, connection model
3 – Describes high-level idea with correct use cases
1 – Confuses them or doesn't know differences

For: Junior, Senior

2. How does DNS resolution work?

Answer:

Check /etc/hosts
Check DNS cache
Query recursive resolver (configured in /etc/resolv.conf)
Resolver queries root → TLD → authoritative DNS
Returns IP to client

dig openai.com
nslookup openai.com

Scorecard:

5 – Explains resolution chain clearly with tools
3 – Describes recursion or lookup vaguely
1 – Thinks it’s hardcoded or local only

For: Junior, Senior

3. What is a socket and how is it used in networking?

Answer:

A socket is an abstraction for a network endpoint (IP + port). Used in inter-process or remote communication.

# Simple TCP server in Python
import socket
s = socket.socket()
s.bind(('0.0.0.0', 8000))
s.listen()

Scorecard:

5 – Understands socket lifecycle and protocols
3 – Knows basic usage
1 – Doesn’t know or confuses with files

For: Junior, Senior

4. What happens when you `curl google.com`?

Answer:

DNS resolution
TCP connection handshake
TLS handshake (HTTPS)
HTTP request (GET /)
Server responds → data printed to stdout

curl -v https://google.com

Scorecard:

5 – Mentions DNS, TCP, TLS, HTTP layers
3 – Partial flow described
1 – Just says “it shows a page”

For: Junior, Senior

5. How do you troubleshoot a network issue between two hosts?

Answer:

Ping test (basic connectivity)
traceroute or mtr to find route issues
Check firewall with telnet, nc, or ss
Use tcpdump or wireshark for packet-level issues

ping <host>
traceroute <host>
nc -zv host port

Scorecard:

5 – Uses structured approach with tools
3 – Uses 1–2 tools only
1 – Guesswork or unclear steps

For: Junior, Senior

6. What is MTU and what problems can it cause?

Answer:

MTU (Maximum Transmission Unit) is the largest packet size sent without fragmentation.

Mismatched MTUs can cause dropped packets or degraded performance (esp. in VPNs or tunnels).

ip link | grep mtu
ping -M do -s 1472 <host>

Scorecard:

5 – Knows MTU concept and troubleshooting
3 – Defines MTU, no impact explanation
1 – Doesn’t know or misuses term

For: Senior

Security

1. What’s the difference between authentication and authorization?

Answer:

Authentication is verifying identity (e.g., username/password).
Authorization is checking if the authenticated user has permission to do something (e.g., access a file).

Think:

AuthN → Who are you?
AuthZ → What can you do?

Scorecard:

5 – Clearly separates both with real-world analogy or example
3 – Understands both but mixes terminology
1 – Uses the terms interchangeably or incorrectly

For: Junior, Senior

2. How do Linux file permissions contribute to system security?

Answer:

They enforce access control via:

Owner, group, others permissions (rwx)
Prevent unauthorized access/modification
Controlled using chmod, chown, and umask

chmod 640 config.yml
chown root:admin config.yml

Scorecard:

5 – Explains use cases like protecting logs, keys
3 – Understands syntax but not implications
1 – Uses chmod/chown without understanding

For: Junior, Senior

3. How would you secure SSH access on a Linux server?

Answer:

Disable root login
Use key-based auth (disable password login)
Change default port
Use fail2ban or rate limiting
Restrict by IP using AllowUsers or firewall

# Disable root login
PermitRootLogin no

# Enforce key auth
PasswordAuthentication no

Scorecard:

5 – Covers config, firewall, key management
3 – Lists 1–2 things
1 – Just says "use SSH"

For: Junior, Senior

4. How do you check which services are listening and which ports are open?

Answer:

ss -tuln
netstat -tuln
nmap localhost

ss and netstat show open ports; nmap scans from external or internal point of view.

Scorecard:

5 – Uses right tools and interprets results
3 – Knows one tool, limited understanding
1 – Confuses outbound vs inbound

For: Junior, Senior

5. What is SELinux/AppArmor and how do they enhance security?

Answer:

They are Mandatory Access Control (MAC) systems.

SELinux/AppArmor enforce fine-grained access policies beyond standard Unix permissions.
Restrict what processes can read/write/execute, regardless of user.

getenforce  # check SELinux status
aa-status   # for AppArmor

Scorecard:

5 – Explains MAC and differences from DAC (file permissions)
3 – Knows they restrict access
1 – Doesn’t know or confuses with firewall

For: Senior

6. How do you securely store secrets in a script or system?

Answer:

Never hard-code secrets into source code.
Use environment variables, encrypted secrets managers (e.g., AWS Secrets Manager, Vault).
Use file permissions or gpg-encrypted files if local.

export DB_PASS=$(aws secretsmanager get-secret-value --secret-id db_pass)

Scorecard:

5 – Understands secret lifecycle and secure practices
3 – Uses env vars or hardcoded with justification
1 – Admits to hardcoding or storing in Git

For: Junior, Senior

Scripting (Python / Shell)

1. How would you write a shell script to monitor disk space and alert if usage > 80%?

Answer:

Use df to check usage and send an alert if over threshold:

#!/bin/bash
THRESHOLD=80
df -h | awk 'NR>1 {print $5 " " $6}' | while read output; do
  usep=$(echo $output | awk '{ print $1}' | tr -d '%')
  partition=$(echo $output | awk '{ print $2}')
  if [ $usep -ge $THRESHOLD ]; then
    echo "Running out of space on $partition ($usep%)"
  fi
done

Scorecard:

5 – Dynamic partitions, parameterized threshold, alert logic
3 – Hardcoded logic, partial check
1 – Doesn’t know df or how to parse it

For: Junior, Senior

2. How does Python handle exception handling and why is it important?

Answer:

Use try-except blocks to handle predictable errors and prevent crashes.

try:
    value = int(input("Enter number: "))
except ValueError:
    print("Invalid input.")

This avoids program termination and allows logging or recovery.

Scorecard:

5 – Knows try/except, can explain error boundaries
3 – Can use syntax but unsure when to use
1 – Doesn't use error handling at all

For: Junior, Senior

3. What are some differences between Bash and Python scripting? When would you choose each?

Answer:

Bash: Great for orchestration, system commands, glue logic
Python: Better for complex logic, data structures, REST APIs

# Bash: quick disk check
df -h

# Python: parse JSON from API
import requests
r = requests.get("https://api.example.com/data")

Scorecard:

5 – Explains purpose-fit choices
3 – Knows one but not when to use the other
1 – Uses everything in one language poorly

For: Junior, Senior

4. How would you parse a large log file in Python to find lines with errors?

Answer:

Read line-by-line for efficiency:

with open("app.log") as f:
    for line in f:
        if "ERROR" in line:
            print(line)

Avoids loading entire file into memory.

Scorecard:

5 – Uses efficient iteration and explains performance
3 – Works but loads whole file
1 – Doesn’t know how to process files

For: Junior, Senior

5. How do you pass arguments to a shell script or Python script?

Answer:

Shell:

echo "Hello $1"
./script.sh World

Python:

import sys
print("Hello", sys.argv[1])

Or better with argparse.

Scorecard:

5 – Uses argparse or positional args clearly
3 – Only hardcodes inputs
1 – Doesn't know how to pass arguments

For: Junior, Senior

6. How would you schedule a script to run every night at midnight?

Answer:

Use cron:

# Edit crontab
crontab -e

# Run at midnight
0 0 * * * /usr/local/bin/myscript.sh >> /var/log/script.log 2>&1

Scorecard:

5 – Correct syntax and redirection
3 – Knows cron but gets time syntax wrong
1 – Doesn’t know cron at all

For: Junior, Senior

Cloud & AWS

1. What is the difference between EC2, S3, and RDS in AWS?

Answer:

EC2: Virtual machines (compute)
S3: Object storage for files/blobs
RDS: Managed relational database (e.g., MySQL, Postgres)

Use case mapping:

EC2 → host apps
S3 → store backups, media
RDS → production-grade SQL DBs without self-managing

Scorecard:

5 – Maps each to real-world use cases
3 – Knows what they are but not when to use
1 – Confuses them or mixes terms

For: Junior, Senior

2. What is an IAM role and how is it different from an IAM user?

Answer:

IAM User: Long-lived identity (username/password, access keys)
IAM Role: Temporary, assumed by services (EC2, Lambda, etc.)

Roles help implement least privilege without hardcoding keys.

aws sts assume-role --role-arn ...

Scorecard:

5 – Explains temp credentials, use in automation
3 – Knows roles are different but not why
1 – Thinks they’re the same

For: Junior, Senior

3. What is an AWS VPC and why is it important?

Answer:

A VPC (Virtual Private Cloud) is a logically isolated network in AWS.

You define:

Subnets (public/private)
Route tables
Security groups and NACLs
Internet gateways/NAT gateways

This gives you control over network access.

Scorecard:

5 – Explains network isolation and control
3 – Understands high-level concept
1 – Thinks it’s just another EC2 type

For: Junior, Senior

4. How would you create an EC2 instance with a specific security group and key pair?

Answer:

Using AWS CLI:

aws ec2 run-instances \
  --image-id ami-1234 \
  --count 1 \
  --instance-type t2.micro \
  --key-name my-key \
  --security-groups my-sec-group

Or via Console with the same inputs.

Scorecard:

5 – CLI and/or Console understanding with right parameters
3 – Knows general steps but not all config
1 – Has never launched one

For: Junior, Senior

5. What’s the difference between a security group and a network ACL in AWS?

Answer:

Security Group: Stateful firewall at instance level
NACL (Network ACL): Stateless firewall at subnet level

Security group remembers connections; NACLs require inbound/outbound rules.

# Example: allow 22 from IP
aws ec2 authorize-security-group-ingress \
  --group-id sg-123456 --protocol tcp --port 22 --cidr 1.2.3.4/32

Scorecard:

5 – Explains stateful/stateless behavior clearly
3 – Knows they are for access control
1 – Confuses or thinks they’re the same

For: Senior

6. How would you set up an auto-scaling group in AWS?

Answer:

Steps:

Create Launch Template
Define Auto Scaling Group (ASG)
Attach target group or ELB
Set scale-in/out policies based on metrics

# CloudWatch scaling
aws autoscaling put-scaling-policy ...

Scorecard:

5 – Understands full lifecycle and policies
3 – Knows basic scaling concept
1 – Never used ASG or confuses with EC2 instance

For: Senior

Ansible & Infrastructure as Code (IaC)

1. What is Ansible and how does it differ from other tools like Terraform or Chef?

Answer:

Ansible is a push-based configuration management tool using YAML playbooks and SSH.
Terraform is declarative IaC for provisioning infrastructure.
Chef is pull-based, uses Ruby DSL, more complex agent model.

Ansible is agentless and great for config tasks (installing packages, deploying code).

Scorecard:

5 – Explains execution model, use case comparison
3 – Knows basic tool usage but not trade-offs
1 – Doesn’t differentiate or confuses with other tools

For: Junior, Senior

2. Write a simple Ansible playbook to install NGINX on a remote host.

Answer:

- name: Install NGINX
  hosts: web
  become: yes
  tasks:
    - name: Install NGINX package
      apt:
        name: nginx
        state: present

Scorecard:

5 – Correct playbook with privilege escalation
3 – Knows tasks and modules, minor syntax errors
1 – Can’t write or understand basic playbook

For: Junior, Senior

3. What is the difference between `roles`, `tasks`, and `handlers` in Ansible?

Answer:

Tasks: Core actions (e.g., install package)
Handlers: Triggered on notify (e.g., restart service)
Roles: Reusable unit (grouping tasks, handlers, vars, templates)

- name: Reload nginx
  service:
    name: nginx
    state: reloaded
  listen: reload_nginx

Scorecard:

5 – Explains how they compose scalable playbooks
3 – Understands usage but mixes terminology
1 – Uses only tasks or misuses handlers

For: Junior, Senior

4. How would you make an Ansible playbook idempotent?

Answer:

Use modules (like apt, copy, template) that check state before acting. Avoid shell unless necessary.

- name: Ensure NGINX is present
  apt:
    name: nginx
    state: present

Avoids re-running if already installed.

Scorecard:

5 – Understands idempotency and implications
3 – Follows examples but not the principle
1 – Writes commands that always change things

For: Junior, Senior

5. How do you manage secrets or sensitive variables in Ansible?

Answer:

Use Ansible Vault to encrypt variables:

ansible-vault encrypt secrets.yml
ansible-playbook site.yml --ask-vault-pass

Alternatively, use ansible-vault with environment variables or HashiCorp Vault integration.

Scorecard:

5 – Knows vault and production-grade practices
3 – Encrypts secrets manually or insecurely
1 – Hardcodes secrets in playbooks

For: Junior, Senior

6. What is the difference between `inventory` and `host_vars` in Ansible?

Answer:

Inventory: List of managed hosts
host_vars: Variables specific to a given host
Can be defined in file-based or dynamic inventory setup.

[web]
web1 ansible_host=192.168.1.10

# host_vars/web1.yml
nginx_port: 8080

Scorecard:

5 – Understands scope and inheritance clearly
3 – Uses inventory but not vars
1 – Doesn’t understand inventory file or variable system

For: Junior, Senior

Advanced Linux Systems – Filesystem, Processes, File Permissions, fstat, fstab, etc.

1. What happens internally when you run a command like `ls` in a shell?

Answer:

The shell parses the command and calls fork() to create a child process.
The child process uses exec() to run /bin/ls.
The kernel handles syscalls like open(), readdir(), and write() for file listing.

fork();
execvp("ls", args);

Scorecard:

5 – Mentions fork/exec, syscalls, file descriptors
3 – Describes at a high level (command, output)
1 – Can’t explain or confuses core parts

For: Junior, Senior

2. What is the difference between hard and soft links?

Answer:

Hard link: Points to the same inode. File continues to exist until all hard links are deleted.
Soft link (symlink): Pointer to another file path.

ln file.txt file_hard
ln -s file.txt file_soft

Scorecard:

5 – Explains inode-level concept with examples
3 – Describes symbolic vs hard link only
1 – Doesn’t know or confuses terms

For: Junior, Senior

3. How does Linux handle process IDs and parent-child processes?

Answer:

Each process has a unique PID; child processes have a PPID of the parent.
ps, pstree show hierarchy.

ps -ef | grep nginx
pstree -p

Scorecard:

5 – Knows about PID, PPID, forking
3 – Understands ps only
1 – Doesn’t know what PPID means

For: Junior, Senior

4. What are file descriptors and how are they used?

Answer:

Integers representing open files:
- 0 = stdin
- 1 = stdout
- 2 = stderr
Used in redirection and syscalls.

echo "Hello" > out.txt  # uses fd 1

Scorecard:

5 – Understands use in syscalls, redirection
3 – Can list but not apply
1 – Thinks they are "file names"

For: Junior, Senior

5. How do permissions work in Linux (rwx, chmod, chown)?

Answer:

Permissions are divided by user/group/other.
chmod changes mode, chown changes ownership.

chmod 755 script.sh
chown user:group script.sh

Scorecard:

5 – Knows permission matrix and security impact
3 – Can set perms but doesn't know what they mean
1 – Doesn't use these commands properly

For: Junior, Senior

6. How do `fstab` and the mount process work?

Answer:

/etc/fstab lists filesystems to auto-mount at boot.
Fields: device, mount point, fs type, options, dump, pass.

# Example line:
UUID=... /data ext4 defaults 0 2

Use mount -a to test.

Scorecard:

5 – Knows all fields and recovery strategies
3 – Knows where fstab is, not full format
1 – Thinks it's dynamic or for user config only

For: Senior

7. What is the purpose of `/proc` and how can it be used to debug processes?

Answer:

Virtual FS exposing kernel and process info.
/proc/<pid>/ contains command, fd, environ, limits, etc.

cat /proc/self/status
ls /proc/$(pidof nginx)/fd

Scorecard:

5 – Can explore running processes, file usage
3 – Knows it exists but unsure of structure
1 – Doesn’t use /proc at all

For: Senior

8. Explain the output of `ls -l` and what the permission bits mean.

Answer:

-rwxr-xr-- 1 user group 1234 Jul 1 10:00 file

rwx: Owner (read/write/execute)
r-x: Group (read/execute)
r--: Others (read)

Scorecard:

5 – Parses each section correctly
3 – Partial understanding
1 – Misinterprets completely

For: Junior, Senior

9. What does `fstat()` do in a C program or from the system’s perspective?

Answer:

fstat() fetches metadata about a file from a file descriptor (not a path).
Used in low-level file inspection.

struct stat st;
fstat(fd, &st);

Scorecard:

5 – Knows when to use over stat(), real use
3 – Knows what it returns
1 – Never heard of it

For: Senior

10. How would you diagnose a file system that is slow or full?

Answer:

Use tools like df -h, du -sh *, iotop, dstat, iostat
Check inode exhaustion: df -i
Look for large logs, deleted files still in use

lsof | grep deleted

Scorecard:

5 – Uses structured tools, knows inode vs space
3 – Looks at space only
1 – Just guesses or reboots

For: Senior

✅ Scorecard Summary Table

Section	Question (Short Description)	For	5 (Excellent)	3 (Adequate)	1 (Weak)
Linux Internals	`ls` execution process	Both	Explains fork, exec, syscalls	General description	Doesn’t understand shell execution
	Hard vs Soft links	Both	Knows inodes, explains persistence	Knows command usage	Confuses the two
	PID and PPID	Both	Knows process hierarchy	Recognizes `ps`, `pstree`	Doesn’t understand process relationship
	File descriptors	Both	Explains std fds and redirection	Lists them, unclear on use	Thinks they are filenames
	File permissions (`chmod`, `chown`)	Both	Understands permission matrix and use cases	Can use commands, unclear on implications	Doesn’t know syntax or impact
	`fstab` structure and mounting	Senior	Knows syntax, fields, mount recovery	Knows file location	Doesn’t know `fstab`
	Using `/proc` to debug processes	Senior	Uses `procfs` tools, knows structure	Knows it exists	Never uses it
	`ls -l` permission bits	Both	Can read and explain each segment	Knows basics	Misreads bits
	`fstat()` syscall	Senior	Explains descriptor-based metadata	Knows similar to `stat()`	Unaware of `fstat()`
	Filesystem diagnostics	Senior	Uses multiple tools + inode checks	Checks disk usage only	Random guesses / reboots

Section	Question (Short Description)	For	5 (Excellent)	3 (Adequate)	1 (Weak)
Scripting	Disk alert script (Shell)	Both	Param-driven, clean logic	Hardcoded, works	Doesn’t know `df` or loops
	Python exceptions	Both	Uses try/except properly	Uses, but unclear on need	Never uses exception handling
	Bash vs Python	Both	Knows when to use each	Knows both but uses one always	Misuses both or doesn’t distinguish
	Parse logs (Python)	Both	Line-by-line, memory efficient	Works, but inefficient	Doesn’t understand file IO
	Script arguments	Both	Uses `argparse`, handles errors	Uses `sys.argv` or `$1`	Hardcodes values
	Scheduling via `cron`	Both	Correct cron syntax, logs output	Knows cron exists	Doesn’t know or use cron

Section	Question (Short Description)	For	5 (Excellent)	3 (Adequate)	1 (Weak)
Cloud & AWS	EC2, S3, RDS difference	Both	Matches use cases to services	Describes basic function	Mixes them up
	IAM Role vs User	Both	Explains roles, automation, no keys	Knows concept, unsure on differences	Thinks they’re same
	What is a VPC	Both	Explains subnets, routing, security	Knows isolated network	Confuses with EC2
	EC2 with SG + Key Pair	Both	Knows CLI/console and inputs	Knows steps but misses detail	Never launched EC2
	SG vs NACL	Senior	Explains stateful/stateless & hierarchy	Knows purpose, not internals	Doesn’t know NACL or uses only SG
	Setup Auto Scaling Group	Senior	Knows templates, scaling policies	Knows concept, not config	Never used or confused

Section	Question (Short Description)	For	5 (Excellent)	3 (Adequate)	1 (Weak)
Ansible & IaC	Ansible vs Terraform vs Chef	Both	Knows tools, models, trade-offs	Basic understanding	Confuses or unaware
	Install NGINX via playbook	Both	Valid playbook, privilege use	Working syntax, some gaps	Can't write playbook
	Roles, Tasks, Handlers	Both	Knows structure, when to use	Uses tasks only	Doesn’t know handlers
	Idempotency in Ansible	Both	Uses proper modules, avoids `shell`	Understands idea	Ignores or misuses
	Secret management with Vault	Both	Uses Vault securely, or external tooling	Encrypts manually	Hardcodes secrets
	Inventory vs host_vars	Both	Understands scope/merge hierarchy	Uses inventory but not vars	Doesn’t know structure

✅ Platform Engineer Shortlisting Rubric

Category	Evaluation Metric	Junior Pass Criteria	Senior Pass Criteria
Linux Internals	File system, processes, syscalls, permissions	Understands basics of `ls`, `chmod`, `ps`, links	Explains syscalls, `fstat`, `/proc`, mount/fstab
Scripting	Shell + Python usage, parsing, cron	Can write basic scripts, knows cron & args	Clean, idiomatic Python/Bash, can optimize logic
Cloud & AWS	Core AWS services, VPC, IAM, scaling	EC2, S3, IAM User vs Role	VPC, SG vs NACL, Auto-scaling, architecture-aware
Ansible & IaC	Playbooks, idempotency, secrets, config mgmt	Can write small playbooks, understands Vault	Modular roles, idempotent, secure and reusable
Depth & Reasoning	Problem-solving, clarity, correctness	Can follow logic, make tradeoffs in scripts	Understands low-level implications, offers better design
Debugging/Diagnosis	Commands, logs, filesystem issues	Uses `df`, `ps`, `top`, `cron`	Uses `iotop`, `lsof`, `procfs`, inode analysis

🎯 Scoring Strategy

Level	Description
5 (Expert)	Teaches others, writes optimized and modular code, handles edge cases, offers trade-offs
3 (Solid)	Solves the task, some minor gaps or less efficient methods
1 (Weak)	Misses key concepts, fumbles basic commands or logic

📊 Rubric Interpretation by Role

Final Score Range (Per Section)	Junior Outcome	Senior Outcome
Mostly 5s	Top-tier Junior, can level up fast	Strong hire, may mentor others
Mix of 3s & 5s	Good hire with room to grow	Acceptable if senior in niche domain
Mostly 3s	Junior hire with structured onboarding	Senior may need support
Any 1s in core areas	Reject or consider for support role	Not suitable for senior

✅ Final Decision Template

You can fill this table after each candidate's interview:

Section	Score (1–5)	Notes
Linux Internals
Scripting
Cloud & AWS
Ansible & IaC
Overall Impression		Communication, clarity, decision-making
Hire Decision	✅ Hire / ❌ Reject / 🤔 Hold

ganapativs/Platform Engineer: Interview Questions(Basics).md Secret

Platform Engineer: Interview Questions(Basics)

Linux Fundamentals

1. What happens internally when you run a command like ls in a shell?

2. How do fork and exec work in Linux, and why are they important?

3. What's the difference between a process and a thread?

4. How can you find which process is using a specific port?

5. Explain what a zombie process is and how to clean it up.

6. How does Linux handle memory allocation (RSS vs Virtual Memory)?

7. What are inodes and how do they relate to files?

8. What’s the difference between a hard link and a symbolic link?

9. How would you check disk I/O performance?

10. What happens if you delete a file that is still open by a process?

11. How do file permissions work in Linux? (chmod, chown, etc.)

12. How does the fstab file work and when is it used?

13. What does the fstat() syscall do and how is it different from stat()?

14. How do you check open files on a system or per-process?

15. How do you monitor real-time file system usage (space and inodes)?

Networking

1. What is the difference between TCP and UDP?

2. How does DNS resolution work?

3. What is a socket and how is it used in networking?

4. What happens when you curl google.com?

5. How do you troubleshoot a network issue between two hosts?

6. What is MTU and what problems can it cause?

Security

1. What’s the difference between authentication and authorization?

2. How do Linux file permissions contribute to system security?

3. How would you secure SSH access on a Linux server?

4. How do you check which services are listening and which ports are open?

5. What is SELinux/AppArmor and how do they enhance security?

6. How do you securely store secrets in a script or system?

Scripting (Python / Shell)

1. How would you write a shell script to monitor disk space and alert if usage > 80%?

2. How does Python handle exception handling and why is it important?

3. What are some differences between Bash and Python scripting? When would you choose each?

4. How would you parse a large log file in Python to find lines with errors?

5. How do you pass arguments to a shell script or Python script?

6. How would you schedule a script to run every night at midnight?

Cloud & AWS

1. What is the difference between EC2, S3, and RDS in AWS?

2. What is an IAM role and how is it different from an IAM user?

3. What is an AWS VPC and why is it important?

4. How would you create an EC2 instance with a specific security group and key pair?

5. What’s the difference between a security group and a network ACL in AWS?

6. How would you set up an auto-scaling group in AWS?

Ansible & Infrastructure as Code (IaC)

1. What is Ansible and how does it differ from other tools like Terraform or Chef?

2. Write a simple Ansible playbook to install NGINX on a remote host.

3. What is the difference between roles, tasks, and handlers in Ansible?

4. How would you make an Ansible playbook idempotent?

5. How do you manage secrets or sensitive variables in Ansible?

6. What is the difference between inventory and host_vars in Ansible?

Advanced Linux Systems – Filesystem, Processes, File Permissions, fstat, fstab, etc.

1. What happens internally when you run a command like ls in a shell?

2. What is the difference between hard and soft links?

3. How does Linux handle process IDs and parent-child processes?

4. What are file descriptors and how are they used?

5. How do permissions work in Linux (rwx, chmod, chown)?

6. How do fstab and the mount process work?

7. What is the purpose of /proc and how can it be used to debug processes?

8. Explain the output of ls -l and what the permission bits mean.

9. What does fstat() do in a C program or from the system’s perspective?

10. How would you diagnose a file system that is slow or full?

✅ Scorecard Summary Table

✅ Platform Engineer Shortlisting Rubric

🎯 Scoring Strategy

📊 Rubric Interpretation by Role

✅ Final Decision Template

1. What happens internally when you run a command like `ls` in a shell?

2. How do `fork` and `exec` work in Linux, and why are they important?

11. How do file permissions work in Linux? (`chmod`, `chown`, etc.)

12. How does the `fstab` file work and when is it used?

13. What does the `fstat()` syscall do and how is it different from `stat()`?

4. What happens when you `curl google.com`?

3. What is the difference between `roles`, `tasks`, and `handlers` in Ansible?

6. What is the difference between `inventory` and `host_vars` in Ansible?

1. What happens internally when you run a command like `ls` in a shell?

6. How do `fstab` and the mount process work?

7. What is the purpose of `/proc` and how can it be used to debug processes?

8. Explain the output of `ls -l` and what the permission bits mean.

9. What does `fstat()` do in a C program or from the system’s perspective?