I was contacted by a recruiter, and the overall process had 7 interview rounds.

• 2 screening rounds
• 5 virtual onsite rounds

After every set of rounds, the recruiter called me and told me what went well and what could be improved. Overall, it was a great experience. All interviewers were friendly and cheerful.

Interviews

Screening

• Round-1 Behavioral/Managerial

  • 1. Describe your current project. How is it challenging?
  • 2. How does your work impact the customer?
  • 3. How do you try to innovate?

• Round-2 Coding

  • 1. Print Fastest to Slowest Dinosaurs (from CSV)
  • 2. Find Battleship in a 2-D matrix

Onsite Interviews

• Round-1 Systems/Unix

  • 1. Signals, interrupts, IVT? SIGINT, SIGTERM. Which signal does kill send?
  • 2. Process memory layout?
  • 3. Stack overflow, heap overflow?
  • 4. How does a system call go from user space to kernel space?

• Round-2 Coding

  • 1. [Mindsweeper grid design]
  • 2. [Can an array be split into 2 halves?]

• Round-3 Design

  • 1. Design a botnet. The botnet can exploit 10,000 low-end machines to run code. All machines need to crawl webpages and return results. No machine should crawl a page again.
    • Interviewer's feedback:
      • a. Candidate is not into system design, not aware about designing large systems.
      • b. Did not come up with a final design.
      • c. I have not written code.
      • d. They need someone with greater exposure to System Design for this position. <<And should be.

• Round-4 Networking

  • 1. What's your favorite protocol (IPsec)?
    • What is its flow?
    • What are its drawbacks/improvements?
  • 2. HTTP/1.2 vs 1.3. Carrying HTTP over UDP?
  • 3. Everything that happens when facebook.com is searched on a browser. DNS, ARP, routing tables, etc.
    • This was an intense interview. The interviewer wanted to ask how the QUIC protocol is better than TLS, specifically TLS over TCP. Why is TCP congestion control a problem and how can we remove it?

• Round-5 System

  • 1. Interprocess Communication mechanisms (Pipes, named pipes, shared memory, message queues, sockets).
    • How do they work internally? Advantages/disadvantages of each, their code.
    • Is data copied into kernel buffers, or does it remain in user space only?
    • Can more than one process write to a pipe at a time?
    • Code for every IPC mechanism, APIs, and their parameters.

• Round-6 Behavioural

• Remember: This is not a technical round. Do not go technical.

  • 1. Tough project.
  • 2. Disagreements in the team.
  • 3. Bad or good manager.

Preparation

• After clearing the screening round, I took 1.5 months for preparation. Material: //Coding: LeetCode coding questions (Facebook specific). //Unix Operating System: Tanenbaum - Modern Operating Systems, 4th Edition. //Networks: Computer Networks - Tanenbaum, 5th Edition. //System Design: Distributed Systems - Tanenbaum, 3rd Edition.

I believe it's best we should read good books instead of reading through the internet.

Best of Luck.