The Tech Interview Behind the Scenes: Kostadin Spiridonov

The Tech Interview Behind the Scenes is an HRLabs series.
Let’s take a look behind the scenes of the technical interview process from the interviewers' perspective.
Our goal is to provide candidates with valuable tips and recommendations directly from professionals who conduct interviews for various technical roles.

“Focus on the concepts and principles rather than the details.” is Kostadin Spiridonov advice, Deputy .NET Department Manager at Coherent Solutions.

Tell us more about your career path.

In 2011, I began my studies at the Natural Sciences and Mathematics High School in Smolyan. A key milestone in my development was participating in the National Olympiads in Information Technology, which sparked my interest in the software industry.

During my studies at Plovdiv University, I started working as a .NET developer at ScaleFocus. Over the years, I have been involved in a variety of projects and companies, allowing me to gain in-depth technical expertise in DevOps, backend development, and .NET. Additionally, I developed team and people management skills, enabling me to combine technical knowledge with leadership competencies.

As a candidate, have you had any strange interviews? What about interviews that impressed you?

For me, an interview is a two-way process, where both parties try to get to know each other as well as possible to make the most informed decision.

One of the strangest interviews I had was for a Senior Developer position. It lasted about 45 minutes, during which I was asked around 30 pre-prepared questions that required short and specific answers. In the end, the evaluation was based solely on the number of correct answers, with no discussion or feedback.

On the other hand, the most impressive interview I have ever attended made me feel like I was already part of the team. Instead of a standard questionnaire, we had an in-depth discussion about my experience and explored real challenges from their work, looking for solutions together. This gave me a clear sense of the company's culture and convinced me that it was a place for learning, teamwork, and professional growth.

What skills and qualities do you look for in a candidate? How can a candidate stand out during the interview?

Two key aspects are crucial for me when evaluating a candidate:

• Presentation of experience – how the candidate describes their projects, the technical challenges they have overcome, and the teamwork they have been involved in.
• Future vision – how the candidate envisions their development, the goals they set for themselves, and what motivates them.

Based on these two components, a comprehensive assessment of the candidate’s profile can be made, covering the full spectrum of their skills.

What questions do you typically ask in technical interviews? Do you have specific tasks or problems that you often use to assess candidates?

The questions and tasks I assign are always related to the candidate’s previous experience. My goal is to understand what decisions they have made and why, as this reveals their thought process and working style beyond the interview setting.

I often place candidates in a different situation based on real-life scenarios to see how they would approach something familiar but modified. 

How important are good communication skills for a candidate? How do they impact the overall interview?

Communication is of critical importance, especially in the IT industry, where we work in international and remote teams. The lack of these skills can lead to serious issues, and unfortunately, it is not something that can be easily learned from online courses.

How important is cultural fit when making a hiring decision? How do you assess whether a candidate will fit well into the team?

This is the most important factor in the selection process. Technical and non-technical skills matter, but cultural fit is the foundation for long-term success and job satisfaction.

What are the most common mistakes candidates make during an interview? What advice would you give candidates on how to prepare for an interview?

The most common mistake is seeing the interview as an exam rather than an opportunity for mutual exploration. Candidates often don’t ask enough questions to determine whether the company and team are the right fit for them.

My advice is to prepare well, showcase their skills, and actively engage in learning about the work environment, projects, and company values.

What advice would you give to candidates who want to improve their technical skills? Are there any resources you would recommend?

Focus on concepts and principles, rather than the details. Use your accumulated experience as a foundation for learning, and don’t be afraid of what you don’t know yet.

Share more about the best (or worst) interviews you've conducted.

One of the most memorable moments in my career was an interview I conducted at the age of 24. The candidate was an architect with 25 years of experience in the industry. An impressive resume, but when we got to the question, "What were your specific responsibilities in the last project listed on your CV (startup personal project)?" his response was:

"We go out for coffee with fellow programmers and discuss the project’s architecture, but it happens no more than once a month. I’m not sure we’ll actually accomplish anything."

How do you evaluate a candidate during an interview—based solely on their theoretical knowledge, or is their approach to solving a problem/task more important to you? What other factors do you consider when making a decision?

Evaluating a candidate during an interview is a complex process and depends on many factors. First and foremost, it’s important for the candidate to have a solid understanding of the technologies they are expected to know, especially for roles where there is not enough time or opportunity for additional training. However, theoretical knowledge alone is not sufficient – the way the candidate approaches a given problem or task is crucial for understanding their analytical and creative abilities.

In addition, cultural fit plays a key role. This includes the candidate’s ability to integrate into the team, communicate effectively, and demonstrate a positive attitude. Human qualities such as willingness to collaborate, a desire to learn, and adaptability are often decisive when making the final decision.