Picture this: You’ve gone through several rounds of screening interviews meant to gauge your cultural fit, experience and soft skills, and now your potential new employer wants to determine the full extent of your technical skills. Welcome to the coding interview.

For many tech pros, the coding interview is a source of dread. They feel like the wrong question can lead to instant failure and total embarrassment. But you don’t need to feel like that: good coding interview prep can alleviate your stress and leave you ready to face your interviewer. We spoke to several technologists to find out how you can best prepare for coding interviews, even if you don’t have much time.

How Long Should a Coding Interview Last?

We tend to think of the coding interview as an all-day excursion into how much you know about coding… and that used to be true. These days, robust coding platforms and open source have reduced the time you spend in coding interviews.

“A coding interview should last between 45 minutes to an hour,” says Michael Muinos, a software engineer at Google.

“This time lets the interviewer check your coding skills, how you solve problems, and how you think,” adds Luis Martinez, web developer at Blue Parrot Software. “In that time, you get to show how you understand problems and find solutions, write code, and explain your ideas.”

Dominic Monn, founder of tech mentorship platform MentorCruise, adds: “This should be enough time [for employers to] get a thorough understanding of a candidate’s coding skills, a basic idea of their problem-solving capabilities, and a general idea of their thought process.”

Luke Shiels, founding design engineer at Delphi, says coding interviews might last an hour, “but we can usually decide to move forward within the first 20 minutes. Intuition is strong, and we can tell if the candidate with thrive or not in a startup environment where they will have less hand-holding available to them.”

While some companies will still subject you to a marathon all-day session, in other words, it seems like just as many are embracing an ethos of “shorter is better.” When in doubt about how to pace yourself, you can always ask your interviewer beforehand about session length; they’ll likely give you an idea of what to expect.

What are Interviewers Looking For in a Coding Interview?

“They want to see how you communicate complex ideas out loud,” Muinos notes. “As a software engineer, this is a very important skill to have. They want to see if you can ask the right questions. Data structure and algorithm problems are difficult and time-consuming and you typically aren't going to know the solution immediately after being given the question. You have to ask questions, define edge cases, and discuss pros and cons with your interviewer which will show that you have strong problem-solving skills.”

One of the most important things an interviewer is looking for is strong coding abilities, Muinos continues: “That is the whole point of these coding interviews after all, so you want to make sure that you are proficient in whatever language of choice you are interviewing in. Lastly, in a coding interview the interviewer will expect you to be able to define the time and space complexity of the algorithm that you implemented. Knowing how to do this makes it obvious to the interviewer that you have good coding fundamentals and can identify how performant code actually is.”

“Interviewers assess candidates beyond technical skills in coding interviews,” says Martinez. “They evaluate problem analysis, solution design, and strategy adaptation abilities. Explaining thought processes and decision rationale is crucial. It shows problem-solving and communication proficiency. Furthermore, interviewers value feedback receptiveness and growth potential.”

These soft skills are as important as technical expertise, Martinez cautions: “Interviewers look for candidates who can dissect problems, devise effective solutions, and pivot approaches when needed. Clearly articulating their reasoning is vital. It provides insight into their problem-solving and communication capabilities. Additionally, interviewers appreciate candidates open to feedback and demonstrating potential for continued growth. These qualities are often considered equally important as technical proficiency.”

What 3-5 Things Can You Do to Prepare for a Coding Interview?

“Demonstrate that you're a lifelong learner,” Monn reminds us. “As a mentoring coach, I always emphasize how valuable this quality is for potential employers because it shows that you're constantly on the lookout to up skill and improve your current skill set. Share recent learnings or a recent topic that you're passionate about to show your enthusiasm.”

To that end: research the company's tech stack. tailor your preparation to the relevant languages and frameworks they are using.

“Contribute to open-source projects to build a relevant portfolio,” Monn continues. “Check what available open-source projects are available that are relevant to the company's tech stack. This will demonstrate initiative and offer real-world examples of what you can do. It's also something that you can include in your portfolio.”

Muinoz adds: “The first thing you can do to prepare for coding interviews is to practice data structure and algorithm problems found on popular websites like Leetcode. In a coding interview, there are many different topics that an interviewer could ask you: trees, graphs, strings, arrays, heaps, dynamic programming, and much more. Practicing problems across all of these topics is a necessity if you want to perform well in the interview.”

The second thing you can do to prepare: mock interviews. “Have someone else in the software engineering field actually give you a coding question and treat it like a real interview,” Muinoz advises. “Doing this preparation will ease the nerves that you will inevitably feel in actual interview.”

The third thing you can do to prepare: timing yourself for every data structure and algorithm problem that you practice. “Coding interviews are typically an hour at maximum, so you should cap your study sessions at the same time limit,” Muinoz says.

And here’s another recommendation: practice explaining your solutions out loud. An interviewer expects to hear your thought process as you are solving these coding problems. Practicing out loud can help you refine your thought process and ease your jitters.

Can You Fail a Coding Interview and Still Be Hired?

“Interviewers know that interview performance is not everything,” Martinez tells Dice. “They look for candidates who are a good fit for the company. Candidates who stay calm, learn from mistakes, and explain their thought processes well are often considered. Even if the coding challenge is not solved, the way a candidate approaches and adapts to problems matters. The hiring decision depends on attitude as much as technical skills.”

But Shiels has a different mindset when hiring, saying it’s “doubtful” he would hire someone after a failed coding test. “There is a surplus of candidates available to us and not enough time to interview them all, let alone give a second chance,” he says.

Muinos says it’s possible to get hired after a failed coding test, but that it “depends on the company you are interviewing at and the interviewer themselves,” adding: “It usually isn't expected that you must code up the most efficient and perfect solution to the problem. Instead, it is more important that you identify multiple approaches, discuss the pros and cons, and implement a solution that the interviewer is happy with.”

It is totally plausible that you can pass a coding interview by providing a suboptimal algorithm, but with strong communication skills, Muinos continues. “It is also plausible that you can fail a coding interview by providing the most optimal algorithm, but with poor communication skills. The moral of the story is that communication with your interviewer is key.”

Conclusion

A coding interview is always daunting, but with a little prep, you stand a great chance of landing that job you really want. Keep in mind there’s no single way to prepare for a coding interview. Leetcode might be what you need, or simply explaining your ideas and code out loud. Coding interviews come down to execution and explanation, so consider where you’re weakest and build those skills up.