200+ Essential Interview Questions for Linux, Nginx, MySQL, Kafka & Security

Linux Interview Questions (selected)

Disk usage detection using shell scripts

LVS load‑balancing strategies and principles

Understanding LVS modes (NAT, DR) and comparison with Nginx

Keepalived and VRRP concepts, troubleshooting split‑brain scenarios

Zabbix monitoring components, modes, and custom discovery

MySQL master‑slave replication, binlog formats, InnoDB features, security hardening, backup and recovery

Redis threading model, common versions, use cases, persistence, master‑slave replication, sentinel mode, cache avalanche, penetration issues

Kafka concepts: ISR, AR, broker role, Zookeeper importance, follower‑leader synchronization, message loss and duplicate consumption, consumer groups

Nginx Interview Questions (40)

Definition and key features of Nginx

Differences between Nginx and Apache

How Nginx processes HTTP requests and implements reverse proxy

Master and worker processes, load‑balancing algorithms (round‑robin, IP‑hash, least‑conn)

Configuration directives, virtual host setup, location block purpose

Rate limiting, token‑bucket and leaky‑bucket algorithms

Static‑dynamic separation, C10K problem, high‑availability configuration

Common modules, status and sub‑filter directives, handling errors, URL double‑slash handling

Network Security Interview Questions (93)

SQL injection, XSS, CSRF, file upload vulnerabilities and mitigation

DDoS attacks, ARP/RARP protocols, DNS fundamentals, routing protocols (RIP, OSPF)

TCP vs UDP, three‑way handshake, four‑way termination, TLS/SSL basics

Cookies vs session, session work‑flow, CSRF protection strategies

Common HTTP status codes, HTTPS vs HTTP, SSL certificate validation

Network security concepts: firewalls, IDS/IPS, VPN, cloud security, CDN

Privilege escalation techniques on Windows and Linux, security hardening

Penetration testing tools, methodology, common exploits (buffer overflow, SSRF, open‑basedir bypass)