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Hire Software Engineer

Challenging backend questions many candidates will struggle with, and common mistakes when hiring a developer


hire software engineer
Nowadays, a lot of companies are becoming more and more aggressive in their business due to the rapid growth and constant changes in the tech landscape. If you desire to be a frontrunner in the market, then you need to have the right talent in your team to help you grow your company and keep up with the latest changes in tech.
The problem which is getting top-notch talent, even for those with a structured recruitment process, has become a lot more troublesome these days due to the high demand and strong competition. An excellent example would be the scarcity of strong and effective software engineers. Other companies would hire software engineers even if they have mediocre knowledge or limited experience just so they could fill out the headcount and get someone to do the job. It is a common mistake that often leads to poor engineering skills in the development team—something you would not want to have in your business.
Thus, in this article, we will share the common mistakes companies make in the process of hiring developers and some helpful tips for you to avoid it.

Failure to conduct proper research to hire software engineer

One of the most basic things companies often overlook is conducting proper research. Since we are living in the digital age, almost everything is fast-paced and constantly changing. The market rates might have gone higher, the skill requirements may have changed, the technology landscape might have shifted and the project details may need different sets of expertise.
The things relevant earlier may not be relevant now, so if you fail to do your research, you might end up with a set of mismatched employees who struggle to complete projects and deliver unsuccessful and inefficient results. Before recruiting talents, check the latest projects in the market and the type of skill sets needed to complete them. Carry out research about relevant experiences and completed projects, so that you have a basis on what you would look for in candidates.
programmers What you want is someone with the complete package—one with the technical know-how, a clear understanding of business objectives, and a fast workflow process.

Rushing the hiring process

The recruitment process could be compared to baking a cake. If you skip some steps or overlook ingredients, you will end up having a bad cake. Unfortunately, more often than not, companies finish with such poor position because they rushed their hiring process without carefully going through each step or looking at each applicant’s credentials. There are various reasons why they go too fast: some want to hire quickly in order to immediately start on an urgent project.
No matter what the reasons are, companies should not be careless in a task as essential as recruitment. You need to remember that recruitment is a multi-stage process with assessments, interviews, and skill-set tests. If you skip one step or fail to conduct proper tests, you may employ people who are ineffective in their roles.

Carelessness in profile checks

Another common mistake done by companies is being careless in checking applicants’ profiles. Since checking CVs is the first and often the longest step in a recruitment process, it is usually the thing that companies end up rushing because they want to expedite their recruitment without skipping a vital step. But instead of helping their recruitment, companies who do not pay careful attention to the credentials or skip the reference check from previous jobs often get a problematic set of applicants who might not be qualified or have bad work ethics.
Take note: what is written on paper may not live up to the actual knowledge or performance of the applicant. Always read through the credentials carefully and check feedback from previous coworkers and managers so you have a better idea of who is applying for the job.

Mismatch in experience and expectations

“I hired someone with the knowledge and experience but there is still something wrong”. This is a frustrating thing you would hear from companies, even though they went through the correct process of recruitment, they still finish having a weak and underperforming development team.
However, when we looked at it closer, we noticed that though the developers have the knowledge and experience, it does not match the expectations and responsibilities needed for the job. More often than not, those hired have the wrong kind of experience and this is why they eventually turn out to be failing. In order to avoid this, ask about the type of experience the developers have and if they have done a project with a similar niche.
Check if their methods of writing software and knowledge in technologies are up to date and related to the requirements needed for your project. If they mention obsolete methods and technologies, save yourself the time and go check on the next developer.

Failure to test soft skills & rapid prototyping

Testing the technical skills of an applicant is extremely crucial in the recruitment process. This is how you gauge the brainpower and resourcefulness of the developer and how they can solve problems in actual projects. However, these tests are often live-coding sessions or problem-solving challenges that do not completely show soft skills or rapid prototyping ability of applicants.
As a result, companies turn out to be getting ineffective and hard to work with technical people. You do not want that. What you want is someone with the complete package—one with the technical know-how, a clear understanding of business objectives and a fast workflow process. To get that, be sure to include an assessment of the applicant’s soft skills, business skills, and rapid prototyping skills in your recruitment stage, whether it be in a form of interview or test. You can check how companies like DevsData incorporated non-technical skills in their recruitment process for their engineering roles.

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Selecting cheap talent to save money

They say good things come with a price and apparently, so do developers. Yet some companies do not want to invest in high-quality developers and engineers because they are more concerned with saving money. Such poor approach often results in greater issues like failed or delayed projects.
Some businesses end up paying more as a result of this and others even end up losing clients. Do not fall for the same mistake. Prior to anything else, you should already know that hiring well-skilled developers would cost you more, so you need to have an allocated budget for it earlier on. Think of these employees as an investment for your business. However, do not worry! Even though hiring high-caliber professionals with experience and knowledge comes with a more expensive price tag, they also have better performance so you are sure to get your ROI.
Man laptop Be sure to include an assessment of the applicant’s soft skills, business skills, and rapid prototyping skills in your recruitment stage, whether it be in a form of interview or test.

Examples of challenging back-end questions

Can you explain what is a SQL injection?

SQL injection usually occurs when you ask a user for input, like their nick, name, password, etc., and instead of this, the user gives you an SQL code statement that will run on your database. For example, he could use a trick involving a single quote and add additional OR statement, which is always true.

What is the difference between undefined, NaN and null?

  • Undefined – the default value used when accessing things that don’t exist. It means that the object doesn’t have any value. This occurs when you create a variable and don’t assign any value to it.
  • Null – object is empty and isn’t pointing to any memory address.
  • NaN – represents a value that is “not a number”. There are many ways that you can generate this error, among others invalid math operations such as 0/0 or “some text” / 1.

You are about to write a backend Node.JS module that will be preprocessing financial information and financial data. What are the potential pitfalls that you foresee? We’re talking just about JS and programming, not strictly about security.

The main potential pitfall is handling monetary values as float precision numbers. It’s a bad idea because a binary representation of a base 10 system, you end up with inaccurate results when you try to do the math. As you calculate more values, the imperceptible precision errors lead to larger gaps. This inevitably ends up causing rounding issues. One of the solutions is to store monetary values as sub-units, which means you need to convert main-units to sub-units (e. g. convert 1 dollar to 100 cents).

You are working with a junior software developer, and the guy accidentally removed the local git branch with all his change. He did not push anything to the origin. Can we do anything to get the changes back?

You should be able to do a git reflog and find the SHA for the last commit of your deleted branch. The next step is to use git checkout command with SHA as a parameter. Now you are at that commit, you can just git branch and its name to recreate branch.

Explain the concept of middleware in Node.js?

Middleware is a function that receives the request and response objects. That means in the application cycle of request and response, these functions get access to all request and response objects with the next cycle function. The next function is represented by the help variable (usually named next). The main tasks of middleware functions are to modify the request or response objects, finish the request-response cycle or invoke the next middleware.

Explain “use strict”

The purpose of “use strict” is to indicate that the code should be executed in “strict mode”.With strict mode, you can not, for example, use undeclared variables. Strict mode makes it easier to write “secure”. As an example, in normal JavaScript, mistyping a variable name creates a new global variable. In strict mode, this will throw an error, making it impossible to accidentally create a global variable. In strict mode, any assignment to a non-writable property, a getter-only property, a non-existing property, a non-existing variable, or a non-existing object, will throw an error.
Man and women looking at a laptop Research about the trends, follow your trusted multi-stage recruitment process, and prepare for different situations that might arise.


Looking at the mistakes done by different companies, the common thing connecting them all together is their rashness and negligence, which led to failure. If you want to avoid going through the same ordeal and hire software engineer just remember to do three basic things: research, follow, and prepare. Read a lot about the trends, follow your trusted multi-stage recruitment process, and prepare for various situations that might arise. It may not guarantee a fast recruitment process, but it would definitely give you a quality pool of engineers that will make up your top-notch development team.

Any questions or comments? Let me know on Twitter/X.

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Tom Potanski Managing Director

Passionate and experienced technology leader. Combining business and technology, helping American clients find exceptional technical talent in Europe and Latin America.

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DevsData is a boutique tech recruitment and software agency. Develop your software project with veteran engineers or scale up an in-house tech team with developers with relevant industry experience.

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“DevsData LLC is truly exceptional – their backend developers are some of the best I’ve ever worked with.”


Nicholas Johnson


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“I interviewed about a dozen different firms. DevsData LLC is truly exceptional – their backend developers are some of the best I’ve ever worked with. I’ve worked with a lot of very well-qualified developers, locally in San Francisco, and remotely, so that is not a compliment I offer lightly. I appreciate their depth of knowledge and their ability to get things done quickly. “


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