Google Data Center Technician L3 Interview Preparation

Posted on May 12, 2026 in Technology

Google Data Center Technician L3: Master Interview Cheat Sheet

The Interview Process

  • Stage 1: Recruiter Screen
    • Background check, location confirmation, and basic fit questions.
    • Common questions: “Why Google?”, “Are you OK with shift work?”, “Can you relocate?”
    • Takes ~46 days on average from application to hire.
  • Stage 2: Technical Phone Screen
    • Rapid-fire fundamentals: protocols, commands, and definitions.
    • 20-30 questions; short answers expected.
    • No NDA; questions are mostly public knowledge basics.
  • Stage 3: Technical Interview with DC Technician
    • Scenario-based: “What would you do if…”
    • Thinking out loud is better than giving a perfect answer.
    • Tests: systematic thinking, escalation judgment, and documentation habits.

Google Values Most

  • Intellectual honesty: Say “I’d verify that” rather than guessing.
  • Systematic troubleshooting: Layer by layer, not random reboots.
  • Escalation awareness: Know when to call for help.
  • Documentation habit: Ticket before action, log after.
  • Safety first: Always mention ESD, LOTO, and PPE.

Confirmed Real Google Interview Questions & Answers

  • Q: What protocol does ping use? A: ICMP (Not TCP or UDP).
  • Q: First SATA disk in Linux? A: /dev/sda (first partition = /dev/sda1).
  • Q: Create EXT4 on first partition? A: mkfs.ext4 /dev/sda1
  • Q: Class B subnet mask? A: 255.255.0.0
  • Q: Default Cisco console baud rate? A: 9600
  • Q: Cat5 max transmission length? A: 100 meters
  • Q: What is RJ45? A: The Ethernet plug name.
  • Q: What is a MAC address? A: Media Access Control — unique hardware ID per NIC.
  • Q: What is BIOS? A: Basic Input/Output System — initializes hardware, runs POST.
  • Q: What is ROM? A: Read Only Memory — stores firmware.
  • Q: What port does HTTP use? A: 80
  • Q: What does NIC stand for? A: Network Interface Card.
  • Q: What does HTTP stand for? A: HyperText Transfer Protocol.
  • Q: > vs >> in bash? A: > overwrites file, >> appends to file.
  • Q: Kernel version command? A: uname -r
  • Q: Where are logs in Linux? A: /var/log
  • Q: IP info command Linux vs Windows? A: ip addr / ifconfig vs ipconfig.
  • Q: Difference between PCIe and PCI? A: PCIe is serial, faster, newer, different slot, and incompatible.
  • Q: How to recognize a failing HDD without software? A: Listen for clicking/ticking, check fault LEDs, feel vibration.
  • Q: What are all server components? A: Chassis, motherboard, PSU (x2), CPU (x2), RAM, HDDs, RAID controller, backplane, NICs, fans, BMC/iDRAC.
  • Q: How to see boot events in Linux? A: dmesg and /var/log/syslog.
  • Q: How to mount a disk? A: mount /dev/sda1 /mnt
  • Q: How to make mount survive reboot? A: Add entry to /etc/fstab.
  • Q: How to image PCs at scale? A: PXE boot.

OSI Model

LayerNameWhat lives here
7ApplicationHTTP, HTTPS, DNS, SSH, FTP, SMTP
6PresentationEncoding, encryption, TLS/SSL, compression
5SessionSessions between hosts, NetBIOS
4TransportTCP, UDP, ports, flow control
3NetworkIP, ICMP, routing, routers
2Data LinkMAC, ARP, switches, VLANs, Ethernet frames
1PhysicalCables, fiber, NICs, hubs, signals, RJ45

Mnemonic (top to bottom): All People Seem To Need Data Processing.

Networking Protocols

  • TCP: Connection-oriented, reliable, ordered (SSH, HTTP, HTTPS).
  • UDP: Connectionless, fast, no guarantee (DNS, SNMP, syslog).
  • ICMP: Used by ping and traceroute.
  • ARP: Maps IP to MAC on local subnet.
  • DNS: Hostname to IP, uses UDP port 53.
  • DHCP: Auto IP assignment (DORA: Discover, Offer, Request, Acknowledge).
  • BGP: Routing protocol between autonomous systems.
  • SNMP: Network device monitoring, UDP port 161.
  • STP: Spanning Tree Protocol, prevents L2 loops.
  • LACP: 802.3ad, link aggregation (NIC bonding Mode 4).

Essential Ports

  • 22: SSH | 80: HTTP | 443: HTTPS
  • 53: DNS | 25: SMTP | 3389: RDP
  • 161: SNMP | 21: FTP | 23: Telnet
  • 67/68: DHCP | 3306: MySQL | 5432: PostgreSQL
  • 8080: HTTP-alt | 2049: NFS | 445: SMB/CIFS

Subnetting Basics

  • /24: 255.255.255.0 (254 hosts)
  • /16: 255.255.0.0 (65,534 hosts)
  • /8: 255.0.0.0 (16M+ hosts)
  • Rule: Every +1 on prefix cuts hosts in half.

Linux System Commands

  • System Info: uname -r, df -h, free -h, lshw, lsblk.
  • Processes: top, ps aux, kill -15, kill -9.
  • Permissions: chmod, chown, ls -la.
  • Logs: dmesg, tail -f /var/log/syslog, journalctl.
  • Services: systemctl (start, stop, restart, enable, disable).

Hardware & Data Center Concepts

  • BMC/iDRAC: Out-of-band management.
  • RAID: 0 (speed), 1 (mirror), 5 (parity), 10 (stripe+mirror).
  • ESD: Electrostatic Discharge protection (wrist straps, mats).
  • LOTO: Lockout/Tagout for powered equipment.
  • PUE: Power Usage Effectiveness (Total power / IT power).

Behavioral: STAR Method

Format every story: Situation → Task → Action → Result.

  • Focus on checking logs before hardware, escalating appropriately, and owning mistakes.
  • Avoid: “I just rebooted it,” “I figured it out alone,” or blaming others.

Day-of Interview Reminders

  • Dress business casual.
  • Arrive early for security clearance.
  • Think out loud.
  • If you don’t know an answer, state your approach to finding the solution using documentation or runbooks.