Phone Screening Preparation (My Path to SRM)

According to Google receives 2 million applications per year. An average year has about 260 working days. That leaves us with over 7500 applications per day. Getting and maintaining recruiter attention is crucial to make it through to the next stage.

If a resume catches the recruiter’s attention they will usually arrange a phone call. The phone call is mostly to get in touch and discuss the process in general. The other function of the first phone call is to discuss the timeline for future interviews, e.g. phone interview(s) and on-site interviews. I was able to share my idea of the timeline and synchronize it with the recruiter. I asked for a slowdown of the process since I felt I needed a bit more time to prepare before heading into the first interview.

Phone screening calls often end with a few minutes of quiz-like questions. I have personally experienced this when I interviewed with Google and Facebook. At eGym I regularly sat down with Human Resources to go over our own little quiz and update the questions we asked. I have heard from other companies that they do phone screening quizzes as well.

No interview should be treated as “informal” […]. Screening starts from the first call.

Sangeeta Narayan, former Executive Recruiter at Google

The purpose of phone screening questions is to help recruiters identify candidates that have a higher chance in performing in later stages of the interview process. Often there is a short answer that requires no or little explanation from either side. The questions are not designed to spark a discussion but to provide a quick overview of a candidates strong and weak areas. Many questions are simple knowledge questions. That is great news! It means one can learn the underlying topics and prepare for the phone screening without having to go through intensive phases of knowledge application. In the phone screening stage knowledge scores more points than experience and skills. This changes at later stages, obviously.

I had a slight advantage because I worked on screening questions in my day job. I also managed to find examples of questions asked at various companies through googling, often on pages 3+. Apparently, there is more than a single page of results. 🤯

Here are some questions I found on the web:

  • What’s a priority queue?
  • Can DNS use TCP? In which cases DNS uses TCP?
  • How does 3 way handshake work in TCP?
  • What’s void *?
  • What’s the system call for creating files?

Big-O Complexity Chart by

I went through several blog posts and Quora answers to identify the broader areas that are covered in the screening quizzes:

  • System calls, most importantly the popular ones like fork(), creat(), open(), read(), write(), exec(), stat(), but sometimes also less popular ones like sbrk() or mmap().
  • General memory management, e.g. what does malloc() do internally and how to re-allocate and free memory.
  • File system internals, like the role of inode or dentry.
  • The lifecycle and the state of processes.
  • Possibly a bit of scheduling and context switching but less likely the nitty gritty details in that area.
  • Signaling and some details on how to send and catch signals. Which signals there are and if a particular signal is even visible to a process or is being handled at kernel level.
  • All sorts 😉of sorting algorithms and their complexity. Stuff that we can find on the Big-O Cheat Sheet mostly.
  • Networking basics, e.g. address and important field properties of popular protocols (Ethernet, IPv4, IPv6, TCP, UDP)
  • IPv4 and IPv6 subnetting
  • Possibly some out-of-the-hip shooting to well-known problems. For example the question could be There’s an array of 10,000 16​bit values, how do you count the bits most efficiently? and a good answer is to use an 8-bit lookup table or the Kernighan algorithm
  • The basics of object oriented programming languages.
  • What differentiates (statically) typed from untyped languages and how to cast types.

I collected as many questions I could find and even came up with my own questions. Then I answered them on a sheet of paper and read through it a couple of times in the days preceding the recruiter call. During the call I was able to answer most of the questions quickly and I believe a good chunk of them also correctly. Although the questions were different from my prepared questions it helped a lot that I researched the answers and brushed up on basics.


If you have just read the above list of topics and feel intimidated 😱 by it let add some calibration here. I was interviewed for a senior role and clearly stated expectations of the level of the role to the recruiter. I believe that the questions I got screened with were appropriate for the level I was looking for. I was expected to have more breadth and more depth than a junior engineer. I claimed 15+ years of working more or less closely with communication or Internet technology. I would expect everyone to get screened at a level that takes into account expertise and seniority stated in the resume. Another reason why lying in the resume just doesn’t pay. You’ll be fine!

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