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Common problem areas I’ve seen after conducting over 600 interviews



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Hey, Aline (founder of right here. Here’s the 2nd put up in our Guest Author sequence The first put up talked about red flags that you must detect while interviewing with firms. Complementarily, this put up, authored by indubitably one of our prolific, long-time interviewers, explores recurring missteps that interviewees make.

One of the vital issues I’m most brooding about with the Guest Author sequence is the diversity of opinions it’s bringing to our weblog. Technical interviewing and hiring is fraught with controversy, and now not the whole lot these posts comprise would possibly be basically based totally on my opinions or the splendid opinions of However that’s what’s wide about it. After over a decade on this industry, I composed don’t reflect there’s a factual technique to behavior interviews, and I reflect hiring is continuously going to be a cramped little bit of a huge quantity because it’s a basically human job. Even supposing we don’t continuously agree, I raise out promise that the voice material we establish forth would possibly be curated, smartly-behaved quality, and written by perfect other folks that are fervent about this house.

Whenever you happen to would possibly comprise solid opinions about interviewing or hiring that you’ve been itching to write about, we’d favor to hear from you. Please electronic mail me at to acquire started.

William Ian Douglas goes by “Ian”, and uses he/him pronouns. He lives within the Denver, Colorado command and graduated from a Computer Engineering program in 1996. His occupation spans reduction-terminate systems, API structure, DevOps/DBA responsibilities and security, and has been a group lead managing tiny groups, and Director of Engineering. Ian branched out into professional technical interview educating in 2014, and in 2017 pivoted his whole occupation to educating instrument construction for the Turing College of Utility & Affect within the Denver site. He joined as a contract interviewer within the summer of 2017 and is a safe fan of the info analytics weblog posts that IIO produces to befriend say and build away with bias in our tech industry interviews. Ian writes technical educating recordsdata at and that you must attain him on Twitter, LinkedIn and GitHub.

I lately conducted my 600th interview on (IIO). I’d favor to portion classes realized, why I come interviews the fashion that I raise out, and shed some gentle on recurring anguish areas I take a look at out happen in technical interviews. Every interviewer on the platform is varied, and so your results would possibly fluctuate. We comprise some very goal appropriate of us serving to out on the platform, and comprise an smartly-behaved community working to better ourselves.

The Mock Interview

All the contrivance in which by our interviews on IIO, we price other folks on three 4-level scales. A secure of 1 formula they did extremely poorly, and a 4 formula they did extremely successfully in that class. I on the total inaugurate my interview the establish all individuals will get 3 out of 4 facets factual away, and then make/lose facets because the interview goes on.

Every interviewer on the platform will comprise some facet that they favor over others. My very own bias as an interviewer tends to be spherical verbal exchange and anguish solving, which I’ll say below.

Technical Abilities

In this class, I grade a candidate on how proficient they appear in their language of preference, whether that they had critical complications coding an algorithm of a particular fashion, if I vital to present a gigantic selection of hints throughout coding.

Narrate Fixing

Here, I grade a candidate on how successfully they rupture the anguish into smaller pieces, give you a come for solving the smaller complications, and likewise debugging complications along the fashion. The capability to mirror by complications while debugging is suitable as most indispensable as writing the code within the first establish. Are they stumped when an issue occurs, or are they in a station to acquire the root trigger on their very own?

Verbal exchange

Interviewers in actuality would love to hear your decision-making job. Here’s also very most indispensable when debugging code. I tended to rent of us who would fit in successfully on smaller groups or clusters of builders. With that in mind, collaboration and simple verbal exchange are an correct technique to win me over.

Fashioned Narrate Areas I Detect in Interviews

Listed below are the tip anguish areas I take a look at out in interviews, now not appropriate on IIO, nonetheless customarily. I hope you mark this recommendation staunch.

Fashioned Narrate Dwelling 1: Jumping into code too soon

I take a look at out this in builders of all types and phases, nonetheless largely within the “intermediate” stage of 2-5 years of ride. They hear an issue, talk about about a high-stage make for 30 seconds or less, and are wanting to acquire coding. They feel treasure they’re on a timer. They want to bustle to acquire issues done. It’s a bustle to the raise out line. First one across the raise out line is the winner.



Please, gradual down. Conception your work. And portion your thought job along the fashion.

Of us that own time to mirror out a mid-stage make, whether that’s pseudocode or appropriate writing out notes of their come, are susceptible to utilize less time debugging their code later. Of us who soar factual into coding plunge into what I call “make-as-you-trot” complications, the establish you’re spending many of time refactoring your code because that you must presumably like to change a parameter handed or a return price, or wait, that loop is within the immoral establish, etc.. Here’s terribly easy to situation as an interviewer.

Spending some time on mid-stage make doesn’t guarantee your success, nonetheless it can establish you time within the raze by thinking by your design a cramped deeper, and that beyond regular time you find is susceptible to be extinct to repair complications later.

Additionally, as an interviewer, I would love to mark you be successful. Namely should always you’re “on-site” (in particular person, or some distance-off for the time being) because you’re costing our firm plenty extra cash in an on-site interview job. While I want to be comely to all candidates within the amount of befriend I will give, if I will take a look at out your make sooner than time, and situation a flaw in that make, I will quiz leading questions to info you to the anguish and factual your come earlier.

Whenever you happen to soar straight into code, I in actuality comprise no idea in case your implementation is even going to work, and that’s now not an unlimited establish to position your interviewer. It’s considerable more challenging for me to factual a make should always that you must presumably comprise 100 strains of Java code written before I in actuality mark what’s occurring in your code.

I observed this lack of planning backfire in a unsuitable contrivance in a staunch interview in 2012. The candidate became as soon as dropped at my interview room by someone in HR, requested within the occasion that they would treasure a bottle of water, and promised to come reduction. We launched ourselves and acquired all of the fashion down to the technical anguish. The candidate shared no details, no make, barely talked about a high-stage come, wrote nothing down, and started writing code on a whiteboard. (This could maybe be my 2nd-to-final whiteboard interview I ever conducted, I abominate whiteboard interviews!) HR showed up a cramped while later, knocking loudly on the door, offering the bottle of water and leaving. The candidate, grateful for a drink, uncapped the bottle and started to own a sip when this unpleasant, draining behold came over their face. The distraction of turning in a bottle of water made them fully lose their voice of thought, and I couldn’t befriend them obtain successfully because they hadn’t shared any details with me about their come. They spent several minutes re-thinking the anguish and starting over.

On the “other facet” of this coin, however, that you must utilize “too long” on the make stage and flee out of time to implement your genius design. I’ve viewed candidates talk about by a mid-stage make, then write notes, then manually stroll by an example with these notes to in actuality be sure that their design is an correct one, and now they easiest comprise a cramped while left to in actuality implement the work. Extra facets on verbal exchange, presumably, nonetheless now we must mark some working code, too.

So what’s the accurate come right here?

I on the total suggest training unless you utilize about 5 minutes thinking by high-stage make selections, 5 minutes to design and say the mid-stage make, and then obtain to work on code. The appropriate info right here is that “prepare makes better” — the extra you prepare this make rupture-down and anguish solving, the better you’ll obtain. Extra on this later.

Fashioned Narrate Dwelling 2: Communicating “Half-ideas”

Here’s a time duration I’ve coined through the years, the establish you inaugurate to claim a thought out loud, raise out the idea in your head, and then exchange something about your code. It customarily sounds something treasure this:

“Hmm, I ponder if I would possibly … … … no, by no formula mind, I’ll appropriate raise out this as an different.”

Lend a hand to my bias for verbal exchange.

Interviewers must know what’s occurring in your thought job. It’s most indispensable that thwey understand how you’re making choices. How are you qualifying or disqualifying ideas? Why are you picking to implement something in a particular contrivance? Did you situation a possible anguish in your code? What became as soon as it?

This lacking recordsdata is a hidden treasure to your interviewer. It takes mere seconds to change your verbal exchange to something extra treasure this:

“I ponder if … hmm … successfully, I became as soon as brooding about imposing this as a depth-first-search, nonetheless given a constraint spherical ___ I reflect a better come is susceptible to be ___, what raise out you suspect?”

That took presumably 2 or 3 extra seconds, and you’ve requested for my idea or steal-in, we can preserve in mind potentialities collectively, and now we’re taking part on the job. You already feel treasure my future coworker!

Fashioned Narrate Dwelling 3: No longer asking clarifying questions

An interview anguish I many times quiz as a heat-up query goes something treasure this: 

You would possibly be in a position to comprise a grouping of integer numbers. Write a come that finds two numbers that add up to a given plot price, end straight, and file these numbers. Return two ‘null’ values if nothing is stumbled on.

Here’s an unlimited query that reveals me how you suspect about algorithms and the categories of assumptions you’re making should always you hear an issue.

I’ve been coding for a quite very long time. Since 1982, in actuality. There’s no data structure known as “a grouping” in any language I’ve ever extinct. So what assumptions are you going to make in regards to the anguish?

Most candidates straight exhaust the “grouping” of numbers is in an array. It’s possible you’ll efficiently resolve this anguish by the utilize of an array to retailer your numbers. Your algorithm is often an O(n^2) (n-squared) algorithm because you’ll be iterating over the info in an exponential contrivance: for each and each price, iterate by the the leisure of the values. There’s a extra environment safe technique to resolve this in O(n) time by picking a decided data structure.

Budge forward and quiz your interviewer questions in regards to the anguish. If they declare you to make your own assumptions that’s varied, nonetheless quiz within the occasion that they’re correct assumptions. Ask if there are alternate data gadgets that you’ll be the utilize of as take a look at cases which can affect your algorithm.

Fashioned Narrate Dwelling 4: Assuming your interviewer gadgets your whole principles

Wait, what?

Yeah, you be taught me factual.

Sure, you’re there for the interview, nonetheless you’re there to existing them how you’ll work on the group, and groups work greatest when there could be evident, initiating verbal exchange and a sense of collaboration. Spend the first cramped while of the interview setting expectations, in particular spherical verbal exchange and work job.

There’s nothing immoral with having this roughly chat with your interviewer: “My recurring work job in a technical anguish treasure right here’s to utilize a minute or two thinking quietly in regards to the anguish and writing down notes, I’ll portion these ideas with you in a 2nd to acquire your input. Then, while I code, I are susceptible to work quietly as successfully, nonetheless I’ll be obvious to end now and then to portion my thought job as I am going, and then stroll you via the code extra totally before we flee it the first time. Would that be okay with you, or raise out that you must presumably comprise varied expectations of how you’d treasure me to keep up a correspondence or work by the anguish?”

I promise you’ll blow their mind. Most interviewers won’t be ready for you to own their expectations into consideration treasure this. It reveals that you’ll work successfully on a group. You’re setting the environment the establish you’re advocating for yourself, nonetheless also being thoughtful of others. You’re bringing up your intentions up front, and giving them the different to collaborate on the job.

Fashioned Narrate Dwelling 5: No longer asking for befriend sooner

As your interviewer, I in actuality comprise a tiny quantity of befriend that I’m seemingly in a station to create throughout a technical anguish. I will’t coach you via the whole lot, obviously, nonetheless I’d somewhat come up with a hint, deduct a level on a rubric, and take a look at out you within the raze be successful at the anguish, than to fight silently and chase in circles and make us both feel treasure the interview is a crash of time.

As a talented interviewer and an trainer at a instrument college, I’ve develop into quite correct at asking leading questions to info you to a realization or respond without me providing you with the respond.

It’s okay to admit should always you’re caught. It doesn’t make you a failure, it makes you human. Let your interviewer know what you’re thinking and  the establish you’re having complications. Hear very conscientiously to their response, they would offer a clue to the anguish, or would possibly provide you with extra thorough advice on guidelines on how to proceed.

My Authorized Sources to Piece

When our interviews at IIO are over, I favor to dive into a gigantic selection of ideas on their job and the establish I reflect they would utilize extra prepare to toughen. In total, I utilize 10 to 20 minutes, customarily going well past my one-hour expected time slot, to respond to questions for somebody, and going into extra component on issues. I LOVE to befriend other folks on IIO.

Listed below are a couple of recurring areas of recommendation I offer to of us.

Verbal exchange

There’s nothing worse than being attentive to your own recorded voice. However all IIO interviews are recorded, and I many times declare of us in my ideas and within the evaluate notes I form up later on to hear to the last cramped while of the interview recording to evaluate the ideas I give them. That it’s possible you’ll also end these recordings and dangle a duplicate of your code at any time. (These recordings are pointless to claim internal most to your and your interviewer.)

All the contrivance in which by the playback, hear to your own thought job and the contrivance in which you keep up a correspondence your ideas. As you work by other challenges, obtain a technique to chronicle yourself talking by the anguish out loud if that that you must imagine, and play that reduction for yourself. You’ll obtain better at articulating pudgy and complete ideas.

Narrate Fixing and Mid-Level Affect

The extra recurring prepare web sites treasure HackerRank, CodeWars, LeetCode, etc, are wide for writing a coded algorithm, nonetheless don’t come up with any technique to voice your make job.

I ship my college students to Project Euler. Euler became as soon as a mathematician, so the complications on the online voice material will in total be quite math-heavy, nonetheless that you must exchange the complications to be whatever you’re chuffed building. Whenever you happen to don’t know guidelines on how to calculate a top quantity, that’s magnificent, swap that out for whether a quantity is equally divisible by 17 or something as an different.

I treasure Project Euler because the challenges there are appropriate observe complications. It’s possible you’ll must mirror of the whole lot: the algorithm, which data structure(s) to utilize, and in particular guidelines on how to interrupt the anguish into smaller pieces.

One of my accepted complications is #19 in their archive: counting how many months between January 1901 and December 1999 began on a Sunday. They come up with the preference of days in each and each calendar month, declare you January 1st 1900 is a Monday, and guidelines on how to calculate a soar three hundred and sixty five days. The comfort is up to you.

The extra you say yourself to varied types of complications, the better you’ll obtain at recognizing patterns.

Practice, Practice, Practice

One share of recommendation we give our college students is to prepare each and each technical anguish several instances. Our government director, Jeff Casimir, tells college students to prepare something 10 instances. That feels treasure a safe effort. I plot extra for 3 to 4 instances, and right here’s my reasoning:

The first time you resolve an issue, all you’ve done is resolve the anguish. It’s possible you will need struggled by obvious facets, nonetheless your easiest staunch achievement right here is finishing.

Whenever you happen to erase your work and inaugurate it a 2nd time, that you must reflect of a decided come to solving the anguish, presumably a extra environment safe respond. Per chance now not, nonetheless now not now not up to you’re getting prepare with this roughly anguish.

Now erase your work and raise out it a third time. Then a fourth time. These are the instances should always that you must inaugurate to actively obtain a memory of the technique it takes to resolve this particular anguish. This “muscle memory” will enable you to should always you take a look at out other technical challenges, the establish you’ll inaugurate to situation similarities. “Oh, this appears to be like treasure the knapsack anguish” and because you’ve solved that several instances, the time you own on high stage make and mid-stage make appropriate shortened somewhat plenty.

One of my accepted technical challenges would possibly be solved the utilize of a handful of quite a whole lot of algorithms (DFS, BFS, DP, etc). Whenever you happen to suspect that you must resolve an issue in a the same trend, resolve it 3 or 4 instances with each and each of these algorithms as successfully. You’ll obtain REALLY correct at recognizing similarities, and comprise an unlimited series of ideas to come other technical complications.

Shameless Self-Promotion

I’ve been writing up notes for aspiring original builders at It’s now not complete, nonetheless I in actuality comprise a gigantic selection of my very own ideas on making ready for technical interviews, networking and outreach, resumes and conceal letters, and loads others. I composed comprise a couple of chapters to write about negotiation ways and tender resignations, nonetheless I’m joyful to own ideas from others on the voice material.

I even comprise a day-to-day electronic mail sequence retaining several types of interview questions, nonetheless now not from a level of view of guidelines on how to respond to the questions completely, there are a great deal of sources available to preserve up out that. Instead, I explore questions from an interviewer’s level of view — what am I in actuality asking, what raise out I hope you’ll declare me, what raise out I hope you won’t teach, and loads others. A tiny preview, as an instance: should always you’re requested “Repeat me about yourself” they’re now not in actuality asking to your existence memoir. They’re in actuality asking “Repeat me a abstract of issues about you that can make you a treasured worker right here”.

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