Surviving the all-day tech interview

~ 04 April 2007 ~

UPDATE: Tips for employers can be found here.

If you haven’t endured one yet, you probably will sometime soon. The all-day tech interview is becoming increasingly common at companies large and small, and rightly so. Sussing out a candidate’s genuine qualifications, talent, and attitude solely in a phone screening or one-hour interview is difficult, at best. On the other hand, spend an entire day with a candidate, interviewed by most members of the team, and an employer has a much better shot at making the right hire, while applicants walk away with better knowledge for making an informed employment decision.

I’ve had the opportunity to endure three all-day interviews, the first two with Apple and MSNBC and the last with my current employer. I now sit on the opposite end of the table, participating in these full-day escapades interviewing applicants for design positions (you knew we’re hiring, right?). All things considered, I think I’ve learned a thing or two about them there interviews, and below are a few tips for y’all walking into your first.

Relax, relax, relax. This is by far the best advice I can offer. If you can stay relaxed, you’ll remain more focused, you’ll speak more clearly, you’ll present yourself more confidently. Fancy that, you might even enjoy the experience.

25% - Portfolio. As a creative director during the dotcom boom, I used to hire solely on strength of portfolio. I wanted team members who could knock out killer designs, period. At the time, I didn’t fully understand there was more to a successful user experience than “killer design.” Great design yields meaningful communication, a process which requires adeptness in not only visual aesthetics, but also in human computing principles, problem solving, copywriting, and the like. All of this in addition to the other 75% that follows.

Oh, and another thing: Ask in advance about how you’ll be asked to show portfolio work. In one of the interviews, I showed portfolio work strictly with printed screen grabs. In another, I showed live web samples broadcast on a projector. And in another, I showed no work at all, crazy as it sounds.

25% - Creative thinking. Brace yourself for this. In two of three interviews I was asked to stand and whiteboard wireframes, diagrams, and the like — all on the spot with no preparation beforehand. It was quite unnerving to be honest. But remain relaxed, inquire before diving into solutions, and you’ll probably do well. Probably.

In addition to whiteboarding, expect to be asked questions that test your mental acuity (i.e. brainteasers). You may be asked a question like this:

A light bulb is turned on by one of three switches. The light bulb is in an enclosed room with a single door and no windows. How do you determine which switch turns on the bulb if you can enter the room only once?

Or maybe something more mathematical:

Assuming infinite folding, how many times would you have to fold a phonebook in half to reach the moon?

The point here is not necessarily that you calculate an exact answer, but that you verbalize your process for understanding a problem, gathering information, and exploring possible solutions.

25% - Communication skills. Come prepared to explain how you articulate reasoning for the decisions you make, how you’ve engaged customers in conversation that exposes the needs and wants of their users, how you’ve interacted with team members on challenging projects, etc. Show that you possess not only artistic flair but the ability to foster great relationships.

25% - Team fit. I’ve seen “team fit” — how well you and the team jell — work both for and against applicants, irrespective of portfolio strength. Expect team members who interview you to be asking themselves, “Is this someone I can see myself working with? Someone I’d carpool with? Someone I’d hang with at SXSW?” Seeing the Happy Cog gang interact at AEA Boston was rather inspiring, as they exemplify a team that plays well together. There’s just something about team fit that fosters an environment conducive to getting stuff done. Best advice I can give here is to be yourself, have fun, and of course, relax.

Elevate your demeanor. Your attitude and engagement during the interview process is critical. Don’t feign enthusiasm, but rather remain positive and show interest in the persons interviewing you. Look directly at the eyes and remain confident as you deliver your responses. Ask direct questions. After all, you’re interviewing the company and its management as much as they’re interviewing you.

Good luck, friend. Knowing is half the battle. The other half, well… did I mention brainteasers?



Veer Veer: Visual Elements for Creatives.
Stock photography, type, and killer tees. Genuinely recommended by Authentic Boredom.

1   Wesley Walser ~ 04 April 2007

Well how nice, I am preparing for two of these in the coming week. Mine might be more technical in nature than the three that you have done, as they are development jobs, but the advise is still very relevant and I appreciate all the advice I can get.

Thanks for the nice write up.

2   erat ~ 04 April 2007

Oooh, oooh, I know the lightswitch/lightbulb answer!

I’m not tellin’, though, unless I’m offered lots of money.

3   Michael Dick ~ 04 April 2007

@Erat, are you going to make us (who do not know the answer) Google for it? :).

@Cameron, thanks for the advice, I most like the posts regarding your past/current experiences which in return give us future advice, thanks a lot — I learned a lot.

4   Jesse Bennett-Chamberlain ~ 04 April 2007

I think this post just scared me out of applying for a job. Ever.

5   Adrian ~ 04 April 2007

As one to soon enter the work field, this article is much appreciated. Thanks for the advice and as with Michael, I find your work experience articles most rewarding.

6   Brian Biddle ~ 04 April 2007

Jesse, I agree I was nervous just reading the post…and I’m not even interviewing.

As for the brainteaser, I’d go open the door and then turn the switches on and off. (assuming I could see the door from where the switches are)

7   Cameron Moll ~ 04 April 2007

Oh… once you open the door, you can’t touch the switches after that. (That’s actually part of the question, just didn’t mention it.)

8   Damian ~ 04 April 2007

I’m guessing the switches are in the room?

9   Cameron Moll ~ 04 April 2007


10   greg wood ~ 04 April 2007

If the room has no windows it’s gonna be dark when the bulb is off. So when you flick the switches you’ll be able to tell which one operates the bulb by looking for light escaping at the foot of the door.

Am I close?

As for the moon one, I’d probably just sit there going bright red.

11   Ben ~ 04 April 2007

Thanks for the post, I’m sure it will come in useful. As for the lightbulb question:

If you turn on the lightbulb and leave it for a few minutes, it would heat up.

So, if you try the first switch for a minute, then turn it off. If you then turn the second switch on, and go inside you will be able to know as:
- If the bulb is hot and off, then its switch one.
- If its cool and off then it cant be switch one or two, and has to be switch three?

Need to think about the phonebook question.

12   Dan Mall ~ 04 April 2007

Agreed. We’re hiring, too, and I’d actually say that, for us, the portfolio probably holds a little less weight during the interview. Sure, it gets you in the door, but the other stuff is really what carries you through. Like you said, the “team fit” one is big. If you can’t work like you play, how are you going to love what you do?

Ah, the light bulb teaser. Hot hot heat.

13   David Yeiser ~ 04 April 2007

The moon one is actually a lot less folds than I thought when I first heard this riddle.

Assume the phone book to be 2” thick:

1 fold (1f) = 2 x previous thickness.

1f = 4”
2f = 8”
3f = 16”
4f = 32”
5f = 64”

33f = 17179869180” = 271,147 miles

Distance from the earth to the moon = 238,906 miles.

It’s based on geometric growth, so you can produce a formula that would give you the height of the resulting folds with the variables being the thickness of the phone book and the number of folds.

t0 = original thickness of phone book
f = number of folds
h = height of phone book after folds

h = t0*(2^f)

So for 33 folds:
h = (2)*(2^33) = 17179869180”

Okay, I’m done now. Feel free to delete this comment if it’s too far off-topic!

14   Cameron Moll ~ 04 April 2007

h = t0*(2^f)

very… impressive…

15   Cameron Moll ~ 04 April 2007

the portfolio probably holds a little less weight during the interview. Sure, it gets you in the door, but the other stuff is really what carries you through.

Yes! You’ve articulated what I didn’t — that if you’ve made it through the door, you’ve obviously got the portfolio chops, and now it’s dependent upon character for the most part.

16   Jared ~ 04 April 2007

After all, you’re interviewing the company and its management as much as they’re interviewing you.

Cameron, this is a very important point to make. I can recall a few times where a job looked great on paper, but found during the interview process that the company would not suit me. Not every company has solid grasp on handling web projects, providing proper tools, or even trusting their designers. Remember, the company needs you more than you need them.

As for the light switches, can’t you just turn on all three? One of them is bound to work.

17   Cameron Moll ~ 04 April 2007

Once you open the door to enter the room, game’s over — no more fiddling with switches. How would you know which it was if all 3 were on? (No light escapes under the door.)

18   Jared ~ 04 April 2007

Whoops, I misread the question (doing too many things at once, I thought the objective was turn the light on). I’d say don’t touch the first switch at all. Turn the second switch on for about 30 seconds, then it turn it off. Then flip up the 3rd switch and enter the room. If the bulb was on, then it was the third switch. If the bulb was warm, then it was the second switch. If the bulb off, and cold to the touch, then it was the 1st switch.

19   Nick ~ 04 April 2007

The heat answer seems to be the correct answer, but the best I could come up with before I read the question is this:

1. Turn on first switch
2. Tie a string to the second switch, attach it to the door frame then to the door.
3. Open the door (quickly)
4. If you see the light change - it’s switch 2. If the light was already on - it’s switch 1. If the light remains off - it’s switch 3.

It’s a bit of a hack (maybe attachments to the door aren’t allowed) and you’d have to have a bit of slack in the string to be able to see the light change :)

20   ML ~ 04 April 2007

Not knowing the answer, Jared I think your solution works best (without any tricks). I swear I spent about an hour trying to figure this thing out with no luck. It’s time for a career change.

21   Justin L ~ 04 April 2007

Yeap I’m officially scared of interviews now - I hate riddles!

22   Jim Rutherford ~ 04 April 2007

If only one switch turns on the light to the room you are about to enter, it is likely that two of the switches control the lighting in the room in which you are standing.

23   Allie ~ 04 April 2007

As someone who has gone through two all-day interviews in the past few weeks, I can whole-heartedly agree with everything in this post. The only sidebar I would add is that the “creative thinking” component often involves demonstrating a critical eye — looking at a mock-up or implemented feature and giving usability and design criticism.

I must also admit that the second interview was far less scary than the first even though the second company was more intense, because I’d been through a similar process already. Both interviews had two phases of whiteboarding — one for design (wireframes and diagrams, a little CSS) and one for code — and, during the first interview, I’m fairly certain I started trembling when I was asked to write a sorting algorithm on the board. But once I got rolling, I was able to communicate knowledge without directly demonstrating that knowledge. Can I write a log-base-n sort these days? Probably not. But I can talk about sort efficiency until the cows come home, which hopefully aids in building the communication quotient. And if nothing else, the experience will make the next interview infinitely easier.

24   John ~ 04 April 2007

If I could actually fold the phonebook in the interview, can I have the job??? :P

25   Cameron Moll ~ 04 April 2007

Absolutely :D

26   Sywan ~ 04 April 2007

I always hated the logic questions like the light bulb one. When teachers asked them in school, I’d always make assumptions that teachers would come back and say, “Hey you’re not allowed to do that!” which I would always answer “Why not?”

For instance for the light bulb question. I could do like Ben said and figure it out based on the state of the bulb upon entering by myself.

An alternative answer could be I get someone else to go to that room and meet me. Then I open the door and just start asking them to flip the switches in sequence till we got it.

I always thought and still think that this is a perfectly viable answer since the question is vague and doesn’t state what you can or cannot do. Did the question say or even imply I would be alone? If that were the case it should have stated so.

I just think that the only way there can be 1 correct answer to a question is if the question itself is sufficiently specific and complete.

27   Amit Lamba ~ 04 April 2007

Here’s one for ya:

You have a 3 quart and a 5 quart bucket, an infinite supply of water, how can you measure out exactly 4 quarts of water?

28   Matt ~ 04 April 2007

Die Hard 3 much?

  • fill the 3 quart bottle to the brim
  • fill the 5 quart bottle with the water from the 3 quart bottle
  • fill the 3 quart bottle to the brim
  • fill the 5 quart bottle to the brim from the water in the 3 quart bottle, leaving 1 quart in the 3 quart bottle
  • empty the 5 quart bottle
  • pour the 1 quart of water from the 3 quart to the 5 quarts bottle
  • fill the 3 quart bottle up and pour in the 5 quart bottle, leaving 4 quarts

29   Brian Hildreth ~ 04 April 2007

Great information. And the to solve the lightbulb riddle, its simple. First,
turn the first light switch and leave it on for ten minutes, then turn it off, Second turn on the second light switch and leave it on. Now go into the closet. It light is on, then it is the second switch, If not but the lightbulb is warm, then it is the first switch. If the light is off and the bulb is cool, then it is the third switch.

30   Richard ~ 05 April 2007

You have a 3 quart and a 5 quart bucket, an infinite supply of water, how can you measure out exactly 4 quarts of water?

Assuming the buckets are regular ol’ bucket shaped (i.e. symmetrical):

1. Pour out half the water of each bucket — half of the water will be when the level just reaches the lip of the bucket as you pour it out. (the line of the water will be a diagonal bisection of the bucket)

2. Combine the remaining water.

3. Sit back and watch the competition get all soggy pouring and filling and pouring and filling. :)

31   Michael McLoughlin ~ 05 April 2007

The lightbulb thing… I can’t seem to see the solution (assuming the solution is purely logical, rather than involving the heat of the lightbulb). Before you go in you can have 0,1,2 or 3 of the switches on.

0: Light will be off, and you have no way of knowing which one will turn it on.
1: If the light is on, then you’ve found the switch. Otherwise it could be one of the two switches that is off.
2: If the light is off, then the switch is the one that’s turned off. Otherwise, it could be one of the two that are on, and you don’t know which.
3: Light will be on, and you don’t know which switch turns it on.

Where have I made a mistake?

32   Cameron Moll ~ 05 April 2007

See reply #29

33   Aditya ~ 05 April 2007

Good Post!!
Another Riddle..
If you tell my name, I will be gone! who am I?

34   Michael Dick ~ 05 April 2007

@Aditya, Waldo? :).

35   Amy Noorda ~ 05 April 2007


36   Wes ~ 05 April 2007

A job where a certain religion is a requirement? Is that even legal?

37   Wesley Walser ~ 05 April 2007

@cameron: Ben on reply number 11 was the first to get the bulb problem.

@Wes: I think I have read all of the post and replies and didn’t see anything about a job with religion requirements. Although, I do believe that it is legal for certain organizations (such as churches), but illegal in the case of a for-profit business.

My favorite logic problem is: I have a scale and 7 balls. 1 ball is heavier than all the rest. How do I determine the heaviest ball with only 3 possible weighing attempts?

38   Aditya ~ 06 April 2007

The riddle I asked was in the movie Life is Beautiful. I like that movie a lot :)

Wesley -
Does all the other balls weight same?

39   Cameron Moll ~ 06 April 2007

Although, I do believe that it is legal for certain organizations (such as churches), but illegal in the case of a for-profit business.


Does all the other balls weight same?

Yes (except for the one). But all seven are the same size, color, shape, etc.

40   ~ 06 April 2007

1. Take 3 Balls on left and 3 balls on right and compare them. If the scale doesnt incline on either side then you have the left ball as the heaviest one.
2. If any one side is inclined(meaning heavier) then take the three balls from it, and out of that three pick any two and put it on the either side of scale. If the inclination is not there the 3rd(left out) ball is the heaviest, and otherwise ofcourse the ball on the inclination side is the heaviest.

41   Aditya ~ 06 April 2007

That was me who posted the answer, forgot to mention the name earlier

42   YaaL ~ 06 April 2007

Wesley, 7 balls / one heavier in 3 attempts is dead simple - and it’s solvable in 2 attempts, try with 12 balls / one different (you don’t know whether it’s heavier or lighter) / 3 attempts.

43   Meredith ~ 06 April 2007

I’ve endured a handful now, both at Msft (where I’m at now) and at Real Networks and I have to say that neither are fun, but this is good advice. I didn’t get many of the crazy questions that people always whine about (like the manhole conundrum question), but my interviews have been less about software and more about the web (which Msft seems to care little about, making it difficult for someone who cares about it very much to actually do their job, but I digress). I’ve also endured the weirdest design interviews at vendor companies where it feels like nobody even cares that I have my portfolio on disc ready to hand off or that I have a web site (did, anyway) and no marathon — but I was prepared for the four-hour-minimum onslaught and tag-team of questioning.

At any rate, consider your solid advice seconded from someone who has been under similar fire and landed the gig anyway.

44   Kevin ~ 09 April 2007

Having just gone through a long interview for a consulting position last week the attitude that really helped me was that I was interviewing them as much as they were me. I’ve approached interviews this way in the past and I’ve found that people respond favorably when you show some inquisitiveness regarding their company, their own background, and how they are currently doing things.

I make it a point to ask leading questions and then really listen to what they have to say. Some interviewers will intentionally not respond, don’t get discouraged by that, just press forward confidently with trying to learn more about them and how or if you will fit in at their company.

If you are good at what you do then there are plenty of opportunities out there. You need to ask questions so that you can learn if you are a good for for the corporate culture and with the smaller group you’ll be working with day to day. You’ll spend a large portion of your life working, so you want to be darn sure you enjoy being at work with these people.

You have a lot to offer (or at least you should if you’re interviewing for the position), and they need you, so act like it’s a chat about a partnership of equals instead of you begging to be granted the privilege of working for their company.

45   Amit ~ 10 April 2007

The answer to the bucket question can be seen in comment #28. Comment #30, there are no assumptions made on the shape of the bucket. So, if you follow the route that #28 took, it won’t matter what shape the bucket is.

46   David ~ 11 April 2007

I would agree with Sywan on the brain teasers. There usually is only one “correct” answer, which does not allow for any exploration of trying something different (whether it fails or not). I have come across a few people in my career who were great at these. They also lacked flexibility in their opinions. Design as a business takes a group effort. If you consistently see your answer as the one and only, you would probably be dropped by me.

47   Ed ~ 19 April 2007

Wait, so NorthTemple is not directly connected to the LDS church - but it is a for-profit business? So wouldn’t that make it illegal to have religion as a requirement for a job with NorthTemple?

48   Cameron Moll ~ 20 April 2007

NorthTemple is a blog run by members of the LDS design team, but not endorsed by the church. So essentially we’re hiring for the LDS church but blogging (and reposting the jobs) at NorthTemple.

49   Visitor ~ 31 May 2007

@Wesley Walser: in 2 (!!!) attempts:

>My favorite logic problem is: I have a scale and 7 balls. 1 ball is heavier than all the rest. How do I determine the heaviest ball with only 3 possible weighing attempts?

1. Take 3+3, if their weight is the same — it’s the last one. If not — leave the heavier 3, through the rest away.

2. Now you have 3 balls, and “the one” is among them. Take 1 random ball in your hand, and weight the rest 2 balls. That’s it.

50   Mats Gefvert ~ 03 June 2007

One way of answering the lightbulb brainteaser - and the answer which would probably impress my present employer the most - is to simply go and ask someone who knows.

…and then write down the answer for the next guy who comes along, documenting what you did.

51   Jesse ~ 30 August 2007

Great information! I have one coming up this week and I’m wondering what it will be like.

52   CandyShopGirl ~ 08 October 2007


What do you think about Apple Iogo? >:)


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