5 Common Mistakes in a Technical Interview

Software engineering has become one of the most popular career choices thanks to the latest tech boom. Leading tech firms like Google, Facebook, and Apple have interviewed hundreds of thousands of candidates to acquire the best. Google alone received more than 20,000 resumes a week in 2014. Given the enormous amount of candidates, the company assigns interviews to software engineers on a regular basis. I interview at least one candidate every week and sometimes two candidates during graduation season.

The interview procedure for software engineering candidates composes of two technical phone screenings followed by five on-site interviews. In each 45-minute session, the interviewer states a particular problem, and the candidate writes programming code to solve the problem.

Many of the candidates I interviewed did a great job. They solved the problem, proposed the correct solution, and wrote decent code. However, some of these candidates were not good enough to get the ticket in to the tech giant. What did they do wrong? Here are some red flags during a technical interview.

1. Making things up

Everybody wants to stand out from the competition. Putting additional sauce and spice in a resume is the norm. However, making things up is not the answer.

A candidate I interviewed claimed that he had extensive experience in Big Data. After discovering more details about projects he had worked on, I realized that his experience was entirely different than what he had stated. After receiving the same feedback from other interviewers, the hiring committee decided not going forward with this candidate. Honesty is everything.

2. Giving up quickly

A good software engineer has the spirit of exploration. Sometimes I asked a difficult question to test the candidate’s response instead of looking for a perfect answer. Under high stress during the interview, some candidates thought they failed the test and just gave up without trying.

Surely, no one person knows everything. A good candidate can break the tough questions into smaller pieces, explore possible approaches, and evaluate pros and cons of different ideas. Eventually, they build solutions from these achievable tasks.

3. Being a mine

In a technical interview, the candidate writes programming code to solve a particular problem. Presenting the idea of the approach is as important as the solution itself.

Many skilled candidates are smart and competent in coding but not good at speaking on the spot. I interviewed many candidates who spent the entire session writing codes without saying much. Without communication, it is unlikely to know whether the candidate has the right logic and skill to solve the problem or just happens to know the answer.

4. Overlooking details

In the intense 45-minute session, many things can go wrong. Missing important messages in the details is not a good sign, either. A small error can significantly damage the interview.

It is important to verify the interview question before heading to the answer. Some candidates were overly aggressive. They took the question and worked on the solution right away without checking whether they understood the question completely. It takes just one minor detail to lose a great opportunity.

5. Overusing of fancy terms

Everyone wants to demonstrate their skills and try their best to impress the interviewer. It is fair for the candidate to use professional words as decorations of his or her expertise. However, many candidates put their hope in exaggerated and dazzling vernacular to win the crowd. Fancy words are overkill.

I had interviewed a smart candidate. At the beginning of the session, I gave him a simple question for a warm-up and expected him to solve it within a few minutes. Surprisingly, he spent the entire session analyzing the task with complicated mathematical terms which would only appear in advanced physics classes. The overuse of fancy terms didn’t help him at all.


These red flags may sound like common sense. I have seen many smart candidates making these mistakes, and they have lost their chances. During the stressful interview session, anyone could underperform.

In short, be honest, don’t give up quickly, express your ideas with easy-to-understand phrases, communicate well, and watch out for details. Following the five principles may not guarantee the ticket to big companies, yet it is no doubt that it will help one stand out in the interview.