How to blow your technical interview

Interviewing is a skill. Like any other skill, you need to practice. When I'm interviewing you, I can tell if you've been practicing or not.

Interviewing skills are important, but for a long time, I wasn't really very good at it. I held several positions at my national lab over 20 years, but the interviews were often with colleagues who knew me well. I interviewed candidates for internships at schools and similarly interviewed mostly entry-level candidates for positions in my group.

This did not prepare me for the rounds of technical interviews at my first New York City job with the eccentric billionaire. Somehow I managed to impress them through the two phone screens and two on-site interviews. I got the job, and within a week, I was interviewing new candidates.

I learned a lot about interviewing in that process... Especially what not to do.

We don't really want to hire you

The first thing to know is that my default position about hiring you is: NOT TO!

HR drummed this into me. It was thumbs up or thumbs down -- inclined to hire, not inclined to hire. If someone was very good, you could indicate "strongly inclined to hire" (we had a couple of those). If you were really awful, there was a "hell no!" option as well. Used that a couple of times too.

The phone screen

OK, it's phone screen time. I look at your resume. First problem. There is nothing to talk about. You've blown the interview and I haven't even talked to you yet.

I understand you might be coming right out of school and you might have had an awful internship. But, really, I need something to talk about for 30 minutes.

Don't make me work for it... don't put down your classes. I probably didn't go to your school (or if I did, it was a long time ago!). I don't know what is hard or easy or what.

One guy had a cool FPGA project. Not for a class, not for an internship, he just thought it would be fun. We talked about that. He got the job.

A very interesting woman (in addition to a deep technical resume) had competed in TV cooking shows. We talked about that. She got the job.

The next quick way to blow the interview is to use your mobile phone. The tinny transmissions will annoy the hell out of me just when you need me on your side. Blow it with me and you're out. Please, find a landline.

Remember that the purpose of the phone screen is to see if you are interesting enough to waste 4 or 5 other people's time bringing you in for an on-site.

OK, we chit chatted about some cool projects (you have a couple of those, right?). Maybe I share your hobby, whatever. I still have to ask you something technical. Here's where you need to be on your toes.

Somebody else might ask you a puzzle or algo question. It will vary. Me, I'll ask you about programming languages. You were sent my way because you listed Python or C++ or something and they want to know if you're for real.

That's the next way to blow it.

I was set up for a phone screen with this guy HR was really excited about. They said he was a real Python expert. His headhunter was very excited about him (first warning sign). I started with some interesting language questions. He was stumped (though I could here him desperately googling for answers in the background -- second warning sign). Well, my questions got more and more basic and still all I got was the shoddy answers and the googling.

I pressed a little harder about his background. He said that he taught himself Python. Two weeks ago. The weekend before he sent in his resume. He assured me that he knew everything he needed to know about the language.

I assured him that he did not.

Finally, he admitted that his headhunter told him that it would be good to have Python on his resume.

Hang up. Call HR. Get the recruiter blackballed. Boom!

It is not OK to grossly exaggerate. Don't list something on your resume that you're not prepared to talk about in detail.

Next. Be prepared. The Boy Scouts have it right. I dictated a short piece of code that I wanted a candidate to comment on. I hear a hand muffle the phone and then...

"Mom... Mom! I need some paper right now!!!"

Yep. That went well.

Had another candidate. He didn't Google answers. He asked his office mate for the answers. Yep. Another big winner.

So, to get through the phone screen

• use your resume to guide the conversation
• use a real phone
• don't exaggerate wildly
• be ready to answer questions

On-site

OK, you've managed to talk your way past HR and the phone screener. You're coming on-site. Even if you aced your phone screen, there is plenty of time to blow it.

I phone screened a candidate and thought he was great. He was a chemist/programmer, so I had a chemist friend phone screen him as well. He came for an interview and.... Everyone hated him. Remember that dreaded double thumbs down? He collected a couple of those. The comments said he had no knowledge of any subject whatsoever. Even good ol' Grizzled calls 'em wrong sometimes.

Turns out that he could start a good conversation, but, when pressed for details and fundamentals there was nothing there. He was out the door at lunch.

The next way to blow your interview is to not know the company you're interviewing with. Please, get the name right. Check Google Finance for an overview. It's not that hard.

Those rules about exaggerating your role from the phone screen? They go double here.

Had another great looking (on paper) candidate a few months ago. He described this awesome project that was very similar to what we were looking to do. Got him in a room and asked about the project.

He stumbled over the description. He more or less read back what was on his resume.

My interview partner and I pressed a little harder. What exactly was his part in the project?

In the end, the answer was that he wrote a couple of 50 line scripts in a minor, inconsequential corner of the project.

Don't use that project as the leader on your resume. If you put something there, especially up top. Expect me to ask you lots of questions about it.

Oh... about those questions...

I'm not looking for the quick answer. I'm looking for the deep answer. The simpler sounding the question, the more open it really is.

Another candidate comes in. I have a one hour-long block of time with him first thing in the morning (Grizzled likes to come in early, so he get's all the early slots). I spent that hour asking him open-ended questions and getting the shorted possible answers.

Don't make me work for it. Help me know what you know!

I like to ask a programming question. You claim to be a rock star coder? I want to see some code. It's a fun little word search problem that I have you work out on the board right in front of me. Pick a language any language... I'll follow right along.

One guy. A group leader at a big financial institution. He stares at me like I'm insane. He doesn't want to write code. He wants to talk about writing code. I steer him back to the code. He can't program. He can't program at all. Boom! A double thumbs down.

Different guy. Tries to write the code in Haskell. I guess he was trying to impress me. Only problem is that the candidate clearly doesn’t know Haskell.

Another guy. I give him the rough problem description. I like to leave the description incomplete. I want you to ask me the clarifying questions. I want you to think about edge conditions and what can go wrong.

This guy though, spends the next 44 minutes (yes, I timed it) with his back to me trying to grind his way through the problem. I try to interject, but he says, "NO. I'll get this!" I roll my eyes and work through my latest debugging adventure in my head. In the end, he turns around and pronounces, "It works!"

It doesn't.

More importantly, though, the candidate failed to understand the fundamental nature of the question. I didn't care about the answer (it involved Polonium, but that is another story). I really cared to see how he thought on his feet. I wanted to know what it was like to work with him.

I had my answer. Boom!

Even when you are answering non-programming questions, that advice applies. I was interviewing at a rather famous hedge fund. One of their quants was asking me puzzle and algo questions. I was doing OK, but the questions kept getting harder. And harder. And HARDER! I kept my cool and figured that it was just an attempt to make me break. Eventually, the questions were well beyond my math ability. I said so. The guy says, "great!, you lasted a lot longer than I thought you would!" That was the entire point of the exercise. To make me cry Uncle.

One of my colleagues likes to ask simple questions. The way you approach the answer tells him what "kind" of technical person you are. When I interviewed with him, he showed me a simple loop. I told him that it looked like a SAXPY. So he follows up with optimization questions. A physicist would answer differently. A mathematician another way. A manager would say, "What's that?"

Remember the philosophy. Understand what the interviewer is really asking.

Another way to blow the interview is to be a little too smug for your own good. It's OK to be a little cocky. You need to be sure of yourself, after all. But this guy just leans back and oozes distain for the entire process. It was like he was just negging the whole interview. Weird. He didn't impress me.

When I interviewed at the great vampire squid itself, I had a cool interview. I got asked the typical puzzle and C++ questions, "You have 5 perfectly logical and greedy pirates...", "Please implement a queue using only stacks...", "What are the uses of static in C++", etc.

Well, I start working through the problem. I'm chatting and joking with the interviewer. We're generally having fun with it. He had a good time and the interview flew by. I think if I had memorized these questions and banged out a canned answer, it would not have worked so well (the squid made an offer, but I turned them down).

So, to avoid blowing your interview,

• be ready to answer questions about your resume and the company
• understand what the point of the question is
• try to answer the questions deeply
• have a little fun

Meeting the big boss

My last interview at a prior job was with the eccentric billionaire boss himself. In his big office on the top floor, staring out into the sun setting over Manhattan. This place is notorious for wanting the perfect GPA's from the perfect schools. We get started and one of the first things he wants to know is why I failed out of school. So I tell him. The whole story with no sugar coating. I conclude with how the sting of a large failure really shaped me and made me a better person. I got the job.

The takeaways

It is important to be yourself, warts and all. The interview is a discovery process for each side. With a little work up front, you can really present yourself in the best light. Use your resume to steer the conversation to your strengths. You get to tell the story. You have first initiative. Use it!

Understand that the interviewer just needs something to talk about. It's a conversation. Be an active participant!

Think about why each question is being asked. Don't be afraid to ask for clarification. Questions don't make you seem weak, but stumbling about does. Watching a candidate "get it" when I give them a hint is very rewarding.

Above all though, have some fun. If you don't get this job, there's another one out there. With some practice, you'll be ready.