Question : 1. How did you choose a career in data engineering?

How to answer
The answer to this question helps the interviewer learn more about your education, background and work experience. You might have chosen the data engineering field as a natural continuation of your degree in Computer Science or Information Systems. Maybe you’ve had similar jobs before, or you’re transitioning from an entirely different career field. In any case, don’t shy away from sharing your story and highlighting the skills you’ve gained throughout your studies and professional path.

Answer Example
“Ever since I was a child, I have always had a keen interest in computers. When I reached senior year in high school, I already knew I wanted to pursue a degree in Information Systems. While in college, I took some math and statistics courses which helped me land my first job as a Data Analyst for a large health-care company. However, as much as I liked applying my math and statistical knowledge, I wanted to develop more of my programming and data management skills. That’s when I started looking into data engineering. I talked to experts in the field and took online courses to learn more about it. I discovered it was the ideal career path for my combination of interests and skills. Luckily, within a couple of months,a data engineering position opened up in my company and I had the chance to transfer without a problem.”

Question : 2. What do you think is the hardest aspect of being a data engineer?

How to answer
Smart hiring managers know not all aspects of a job are easy. So, don’t be hesitate to answer this question honestly. You might think Its goal isn’t to make you pinpoint a weakness. But, in fact, what the interviewer wants to know is how you managed to resolve something you struggled with.

Answer Example
“As a data engineer, I’ve mostly struggled with fulfilling the needs of all the departments within the company. Different departments often have conflicting demands. So, balancing them with the capabilities of the company’s infrastructure has been quite challenging. Nevertheless, this has been a valuable learning experience for me, as it’s given me the chance to learn how these departments work and their role in the overall structure of the company.”

Question : 3. Can you think of a time where you experienced an unexpected problem with bringing together data from different sources?

How did you eventually solve it?

How to answer
This question gives you the perfect opportunity to demonstrate your problem-solving skills and how you respond to sudden changes in the plan. The question could be data-engineer specific or a more general one about handling challenges. Even if you don’t have this particular experience, you can still give a satisfactory hypothetical answer.

Answer Example
“In my previous work experience, my team and I have always tried to be prepared for any issues that
may arise during the ETL process. Nevertheless, every once in a while, a problem will occur completely out of the blue. I remember when that happened while I was working for a franchise company. Its system required for data to be collected from various systems and locations. So, when one of the franchises changed their system without prior notification, it created quite a few loading issues for their store’s data. To deal with this issue, first I came up with a short-term solution to get the essential data into the company’s corporate wide-reporting system. Once I took care of that, I started developing a long-term solution to prevent such complications from happening again.”

Question : 4. Data engineers collaborate with Data Architects on a daily basis. What makes your job as a data engineer different?

How to Answer
With this question, the interviewer is most prob-ably trying to see if you understand how job roles differ within a data warehouse team. However, there is no “right” or “wrong” answer to this question. The responsibilities of both data engineers and data architects vary (or overlap) depending on the requirements of the company/database maintenance department you work for.

Answer Example
“Based on my work experience, the differences between the two job roles vary from company to company. Yes, it’s true that data engineers and data architects work closely together. Still, their general responsibilities differ. Data architects are in charge of building the data architecture of the company’s data systems and managing the servers. They see the full picture when it comes to the dissemination of data throughout the company. In contrast, data engineers focus on testing and maintaining of the architecture, rather than on building it. Plus, they make sure that the data available to analysts within the organization is reliable and of the necessary high quality.”

Question : 5. Can you tell us a bit more about the data engineer certifications you have earned?

How to Answer
Certifications prove to your future employer that you’ve invested time and effort to get formal training for a skill, rather than just pick it up on the job. The number of certificates under your belt also shows how dedicated you are to expanding your knowledge and skillset. Recency is also important, as technology in this field is rapidly evolving, and upgrading your skills on a regular basis is vital. However, if you haven’t completed any courses or online certificate programs, you can mention the trainings provided by past employers or the current company you work for. This will indicate that you’re up-to-date with the latest advancements in the data engineering sphere.

Answer Example
“Over the past couple of years, I’ve become a certified Google Professional Data Engineer, and I’ve also earned Cloudera Certified Professional credential as a Data Engineer. I’m always keeping up-to-date with new trainings in the field. I believe that’s the only way to constantly increase my knowledge and upgrade my skillset. Right now, I’m preparing for the IBM Big Data Engineer Certificate Exam. In the meantime, I try to attend big data conferences with recognized speakers, whenever I have the chance.

Question :6. Explain data import in R.

R reads data from a decent number of sources, like text, Excel, SPSS, SAS, Stata, systat… with text, and more specifically, CSV, being the most popular. Depending on the format of the data, you’d need to use different packages to import it into R.In terms of syntax, there is nothing too shocking about the operations – a standard read call is used in most situations.Importing text files is fairly straightforward.The user can use the barebones read.table() function from the built-in {utils} package, and set all relevant arguments, or opt for using read.csv() which has default values for the arguments most often used in importing a CSV file. Both of these would result is you creating a data frame. You could also choose to use the read_csv() from the {tibble} package and import your data as a tibble. That’s the method to be preferred if you’re using R to do data science.Importing Excel files happens with the {xlsx} package.Importing SPSS and SAS data often requires the {Hmisc} package. For .sas7bdat files specifically, Hadley Wickham’s {haven} package can be helpful.Importing Stata and systat data typically hap-pens with R’s {foreign} package.

Question : 7. What is the difference between UNION and UNION ALL?

The UNION command is very similar to the JOIN command, as they are both used to select related information from multiple tables. However, the UNION command selects only columns of the same data type. Furthermore, UNION selects distinct values only, i.e. it combines the result set of two or more SELECT statements. In contrast, UNION ALL selects all values (without eliminating duplicate rows).

Question : 8. What programming/scripting languages have you used?

Which one are you most experienced with?

How to Answer
Generally, job descriptions list the required and preferred programming skills for the role. So, when you talk about the languages you’re most experienced with, make sure you emphasize your work with the preferred/required ones in past projects. In case you lack experience in these, focus on the languages you’re proficient in and list any similarities they may have with the required. And don’t forget to point out that you’re a fast learner that can easily grasp new concepts and languages. This will show the interviewer that you’ll be committed to using the necessary tools, even if you have to complete additional training.

Answer Example
“I have worked with both Python and SQL. How-ever, I’m most comfortable using Python, due to the nature of the tasks in the previous company I worked for. I understand that SQL is preferred, and I can as-sure you I can advance my SQL skills quickly on the job. I’m a quick learner and learning new concepts has always come easy to me.”

Question : 9. Have you ever found a new use for existing data that has brought a positive change in your employer’s business?

How to Answer
A data engineer is often one of the few people who has the broadest view of the company’s data. It’s quite common for departments to work with a limited set of tables within the organization’s data-bases and thus hinder the accuracy of their analyses. That said, a good data engineer should be familiar with the projects and initiatives of each department. This will allow them to provide other employees with valuable insight into what data is available and how they can utilize it to improve the quality of analyses throughout the organization.”

Answer Example
“As a data engineer, it’s important for me to be familiar with all initiatives taken up by the company’s departments. I believe employers should have access to data from other departments in order to improve their work. In my previous job, I proposed to connect employee data with sales data. As it turned out, there was a correlation between the education and work experience of hired employees and high or low sales periods. The subsequent detailed analysis showed that certain employee profiles result in considerable increases in sales for a significant period of time. I take pride in this discovery, as HR data had never been cross-referenced with sales data for analytical purposes in this company before.”

Question : 10. What is your experience in working with data scientists?

What do you think are the common skills you share?

How to Answer
It’s true that data engineers and data scientists have some skills and qualifications in common. It’s also possible that they have some overlap in responsibilities, depending on the requirements of the employer. But, in their essence, their roles are quite different.Data engineers should be aware of the data scientists’ ongoing projects. They handle the maintenance, architecture, and preparation of data for future analysis.Data scientists, on the other hand, rely on the data engineers’ work to extract insights from the data and present the results to management and executives.That said, a hiring manager would like to know how well you understand the work of data scientists and what is your experience interacting with them.

Answer Example
“I’ve had the chance to work with data scientists on many projects and occasions and I can say it’s been a very productive and rewarding experience. We both understand analytics and programming languages which made it easy for me to help them with their projects. The fact that we have overlap-ping skills allowed the data scientists to grasp the limitations of our infrastructure and data availability. At the same time, I was able to easily understand their data needs.”

Question : 11. What is your preferred field of work?

Do you prefer Pipeline or Database, or a more Generalist role?

How to Answer
A data engineer’s role heavily depends on the size of the company and the specific tasks they’re assigned. Generalists employ a variety of skills, as they are responsible for many different tasks. If you’re focused on Pipeline, this means you have experience in working closely with data scientists and have a better understanding of how to prepare data for analysis. Data engineers who have worked mostly in Database, have in-depth knowledge of the ETL process and table schemas. No matter which role/s you have been in, include all your experiences in your answer. You can also go into moderate detail in explaining why you prefer one type over the other.

Answer Example
“I’ve always worked in more of a Generalist role. I can say I like this one more than the other types because I like having a broader scope of expertise. I enjoy being in-the-know about the whole structure and process, as opposed to focusing on just one subset of skills I’ve acquired.”

Question : 12. According to some Big Data professionals, data engineering is a non-analytical career path.

Do you consider this statement true or false? Why?

How to Answer
This statement can’t be interpreted in a single way. Yes, it’s true that compared to a data analyst, a data engineer’s work is much less analytical in nature. However, this doesn’t mean that data engineers lack analytical skills or that they don’t implement them at all. When giving your answer, tell the hiring manager how you view your role as a data engineer and how you’ve used your analytics skills on the job.”

Answer Example
“I’d have to say I firmly disagree with this statement. I’ve used my analytical skills on numerous occasions. As a data engineer, I’ve often performed analyses to ensure the high quality and integrity of the data. My analytical skills have also helped me immensely in my mutual projects with data scientists and data analysts. Thanks to my analytical mindset, I’ve been able to identify and help them with their data needs.”

Question : 13. What trainings would you enroll in to advance your data engineering skills?

How to Answer
Technology’s constantly changing, so, if you’re setting high goals for yourself, this question may prompt you to list several trainings you’d like to fit in your schedule. However, make sure you convey that you’d like to complete these courses as they cover topics of interest and not to make up for weakness-es in your preparation. Balance your answer by mentioning your strengths and the skills you’ve already acquired.

Answer Example
“I think enrolling in trainings is crucial for any data engineer that wants to be up-to-date with the advancements in the industry. Personally, I’d like to expand my current expertise in ETL processes and the cloud environment. Although I have significant experience working with both, I believe my future work can only benefit from continuous learning.”

Question : 1. Which ETL tools have you worked with? Do you have a favorite one? If so, why?

How to Answer
The hiring manager needs to know that you’re no stranger to the ETL process and you have some experience with different ETL tools. So, once you enumerate the tools you’ve worked with and point out the one you favor, make sure to substantiate your preference in a way that demonstrates your expertise in the ETL process.

Answer Example
“I have experience with various ETL tools, such as IBM Infosphere, SAS Data Management, and SAP Data Services. However, if I have to pick one as my favorite, that would be Informatica’s PowerCenter. In my opinion, what makes it the best out there is its efficiency. PowerCenter has a very top performance rate and high flexibility which, I believe, are the most important properties of an ETL tool. They guarantee access to the data and smoothly running business data operations at all times, even if changes in the business or its structure take place.

Question : 2. Have you built data systems using the Hadoop framework?

If so, please describe a particular project you’ve worked on.

How to Answer
Hadoop is a tool that many hiring managers ask about during interviews. You should know that when-ever there’s a specific question like that, it’s highly likely that you’ll be required to use this particular tool on the job. So, to prepare, do your homework and make sure you’re familiar with the languages and tools the company uses. More often than not, you can find that information in the job description. If you’re experienced with the tool, give a detailed explanation of your project to highlight your skills and knowledge of the tool’s capabilities. In case you haven’t worked with this tool, the least you could do is do some research to demonstrate some basic familiarity with the tool’s attributes.

Answer Example
“I’ve used the Hadoop framework while working on a team project focused on increasing data processing efficiency. We chose to implement it because of its ability to increase data processing speeds while, at the same time, preserving quality through its distributed processing. We also decided to implement Hadoop because of its scalability, as the company I worked for expected a considerable increase in its data processing needs over the next few months. In addition, Hadoop is an open-source network which made it the best option, keeping in mind the limited resources for the project. Not to mention that it’s Java-based, so it was easy to use by everyone on the team and no additional training was required.”

Question : 3. Do you have experience with a cloud computing environment?

What are the pros and cons of working in one?

How to Answer
Data engineers are well aware that there are pros and cons to cloud computing. That said, even if you lack prior experience working in cloud computing, you must be able to demonstrate a certain level of understanding of its advantages and shortcomings. This will show the hiring manager that you’re aware of the present technological issues in the industry. Plus, if the position you’re interviewing for requires using a cloud computing environment, the hiring manager will know that you’ve got a basic idea of the possible challenges you might face.

Answer Example
“I haven’t had the chance to work in a cloud computing environment yet. However, I have a good overall idea of its pros and cons. On the plus side, cloud computing is more cost-effective and reliable. Most providers sign agreements that guarantee a high level of service availability which should decrease downtimes to a minimum. On the negative side, the cloud computing environment may compromise data security and privacy, as the data is kept outside the company. Moreover, your control would be limited, as the infrastructure is managed by the service provider. All things considered, cloud computing could be both right or wrong choice for a company, depending on its IT department structure and the resources at hand.”

Question : 4. In your line of work, have you introduced new data analytics applications?

If so, what challenges did you face while introducing and implementing them?

How to Answer
New data applications are high-priced, so introducing such within a company doesn’t happen that often. Nevertheless, when a company decides to in-vest in new data analytics tools, this could turn into quite an ambitious project. The new tools must be connected to the current systems in the company, the employers who are going to use them should be formally trained. Moreover, maintenance of the tools should be administered and carried out on a regular basis. So, if you have prior experience, point out the obstacles you’ve overcome or list some scenarios of what could have gone wrong. In case you lack relevant experience, describe what you know about the process in detail. This will let the hiring manager know that, if a problem arises, you have the basic know-how that would help you through.

Answer Example
“In my last position as a data engineer, I took part in the roll-out of a new data analytics application in my company. Introducing new applications takes careful planning to attempt a smooth transition to the new tool. With my experience, I found that even with careful planning, unforeseen circumstances can occur. In the early stages of the tool’s introduction, we had an unexpected high demand for user licenses. This required reallocation of resources to purchase additional licenses as well as reprioritization of training schedules to meet the needs of different departments. We also had to ensure that our infrastructure could support the significantly higher number of employees utilizing the tool.”“As a data engineer, I’ve taken part in the introduction of a brand-new data analytics application in the last company I’ve worked for. The whole process requires a well-thought-out plan to ensure the smoothest transition possible. However, even the most careful planning can’t rule out unforeseen is-
sues. One of them was the high demand for user licenses which went beyond our expectations. The company had to reallocate financial resources to obtain additional licenses. Furthermore, training schedules had to be set up in a way that doesn’t interrupt the workflow in different departments. In ad-dition, we had to optimize our infrastructure, so that it could support the considerably higher number of users.”

Question : 5. What is your experience level with NoSQL databases?

Tell me about a situation where building a NoSQL database was a better solution than building a relational database.

How to Answer
There are certain pros and cons of using one type of database compared to another. To give the best possible answer, try to showcase your knowledge about each and back it up with an example situation that demonstrates how you have applied (or would apply) your know-how to a real-world project.

Answer Example
“Building a NoSQL database can be beneficial in some situations. Here’s a situation from my experience that first comes to my mind. When the franchise system in the company I worked for was in-creasing in size exponentially, we had to be able to scale up quickly in order to make the most of all the sales and operational data we had on hand. But here’s the thing. Scaling out is the better option, compared to scaling up with bigger servers, when it comes to handling increases data processing loads. Scaling out is also more cost-effective and it’s easier to accomplish through NoSQL databases. The latter can deal with larger volumes of data. And that can be crucial when you need to respond quickly to considerable shifts in data loads in the future. Yes, it’s true that relational databases have better connectivity to various analytics tools. However, as more of those are being developed, there’s definitely a lot more coming from NoSQL databases in the future. That said, the additional training some developers might need is certainly worth it.

Question : 6. What’s your experience with data modeling?

What data modeling tools have you used in your work experience?

How to Answer
As a data engineer, you probably have some experience with data modeling. In your answer, try not only to list the relevant tools you have worked with, but also mention their pros and cons. This question also gives you a chance to highlight your knowledge of data modeling in general.

Answer Example
“I’ve always done my best to be familiar with the data models in the companies I’ve worked for, regardless of my involvement with the data modeling process. This is one of the ways I gain a deeper understanding of the whole system. In my work experience, I’ve utilized Oracle SQL Developer Data Modeler to develop two types of models. Conceptual models for our work with stakeholders, and logical data models which make it possible to define data models, structures and relationships within the database.”

Question : 7. Have you ever taken part in a data disaster recovery situation?

If so, describe what happened and how you solved the issue at hand.

How to Answer
Completing daily assignments is only part of the data engineer’s job. Above all, hiring managers are looking for someone who can quickly respond to urgent situations and contribute to their remedy. Sometimes a data infrastructure may fail. Or data can become inaccessible, lost, or even destroyed. All of these can hurt the company’s processes. So, when answering this question, present yourself as a decisive person with a hands-on approach to solving unforeseen issues.

Answer Example
“In my most recent data engineer job, I was part of a team project focused on developing a Disaster Recovery Strategy. This is how I got familiar with the actions that needed to be taken when we faced a real data disaster recovery situation. A corrupt file somehow got loaded into the company’s system. This caused databases to lock up. As a result, a lot of the data was corrupted as well. What I did was immediately approach the IT team. Together, we made sure our data backups were loaded as quickly as possible, so that the operations in the company can continue to run smoothly.”

Question : 8. Have you ever created custom analytics applications?

If so, please share details about the application you’ve built.

How to Answer
In order to build a custom analytics application, a data engineer should have an in-depth under-standing of the analytic needs of all departments within the company. Creating such applications re-quires careful planning and teamwork. That said, you should answer in a way that highlights not only your programming expertise but also your excellent communication skills.

Answer Example
“The goal of the custom application I built was to marry primary marketing research data with sales data that was stored in the company’s databases. The app helped the Marketing department avoid the tedious process of requesting data from the data warehouse and loading it into Excel. This resulted in a much quicker performance of specific analyses.”

Question : 1. Data maintenance is one of the routine responsibilities of a data engineer.

Describe a time when you encountered an unexpected data maintenance problem that made you search for an out-of-the-box solution”.

How to Answer
Usually, data maintenance is scheduled and covers a particular task list. Therefore, when everything is operating according to plan, the tasks don’t change as often. However, it’s inevitable that an unexpected issue arises every once in a while. As this might cause uncertainty on your end, the hiring manager would like to know how you would deal with such high-pressure situations.

Answer Example
“It’s true that data maintenance may come off as routine. But, in my opinion, it’s always a good idea to closely monitor the specified tasks. And that includes making sure the scripts are executed successfully. Once, while I was conducting an integrity check, I located a corrupt index that could have caused some serious problems in the future. This prompted me to come up with a new maintenance task that prevents corrupt indexes from being added to the company’s databases.”

Question : 2. Data engineers generally work “backstage”.

Do you feel comfortable with that or do you prefer being in the “spotlight”?

How to Answer
The reason why data engineers mostly work “backstage” is that making data available comes much earlier in the data analysis project timeline. That said, c-level executives in the company are usually more interested in the later stages of the work process. More specifically, their goal is to understand the insights that data scientists extract from the data via statistical and machine learning models. So, your answer to this question will tell the hiring manager if you’re only able to work in the spotlight, or if you thrive in both situations.

Answer Example
“As a data engineer, I realize that I do most of my work away from the spotlight. But that has never been that important to me. I believe what matters is my expertise in the field and how it helps the company reach its goals. However, I’m pretty comfort-able being in the spotlight whenever I need to be. For example, if there’s a problem in my department which needs to be addressed by the company executives, I won’t hesitate to bring their attention to it. I think that’s how I can further improve my team’s work and reach better results for the company.”

Question : 3. Do you have experience as a trainer in software, applications, processes or architecture?

If so, what do you consider as the most challenging part?

How to Answer

As a data engineer, you may often be required to train your co-workers on the new processes or systems you’ve created. Or you may have to train new teammates on the already existing architectures and pipelines. As technology is constantly evolving, you might even have to perform recurring trainings to keep everyone on track. That said, when you talk
about a challenge you’ve faced, make sure you let the interviewer know how you handled it.

Answer Example
“Yes, I have experience training both small and large groups of co-workers. I think the most challenging part is to train new employees who already have significant experience in another company. Usually, they’re used to approaching data from an entirely different perspective. And that’s a problem because they struggle to accept the way we handle projects in our company. They’re often very opinionated and it takes time for them to realize there’s more than one solution to a certain problem. However, what usually helps is emphasizing how successful our processes and architecture have proven to be so far. That helps them open their minds to the alternative possibilities out there.”

Question : 4. Have you ever proposed changes to improve data reliability and quality?

Were they eventually implemented? If not, why not?

How to Answer
One of the things hiring managers value most is constant improvements of the existing environment, especially if you initiate those improvements yourself, as opposed to being assigned to do it. So, if you’re a self-starter, definitely point this out. This will showcase your ability to think creatively and the importance you place on the overall company’s success. If you lack such experience, explain what changes you would propose as a data engineer. In case your ideas were not implemented for reasons such as lack of financial resources, you can mention that. However, try to focus on your continuous efforts to find novel ways to improve data quality.

Answer Example
“Data quality and reliability have always been a top priority in my work. While working on a specific project, I discovered some discrepancies and outliers in the data stored in the company’s database. Once I’ve identified several of those, I proposed to develop and implement a data quality process in my department’s routine. This included bi-weekly meetups with coworkers from different departments where we would identify and troubleshoot data is-sues. At first, everyone was worried that this would take too much time off their current projects. How-ever, in time, it turned out it was worth it. The new process prevented the occurrence of larger (and more costly) issues in the future.

Question : 5. Have you ever played an active role in solving a business problem through the innovative use of existing data?

How to Answer
Hiring managers are looking for self-motivated people who are eager to contribute to the success of a project. Try to give an example where you came up with a project idea or you took charge of a project. It’s best if you point out what novel solution you pro-posed, instead of focusing on a detailed description of the problem you had to deal with.

Answer Example
“In the last company I worked for, I took an active part in a project that aimed to identify the reason’s for the high employee turnover rate. I started by closely observing data from other areas of the company, such as Marketing, Finance, and Operations. This helped me find some high correlations of data in these key areas with employee turnover rates. Then, I collaborated with the analysts in those departments to gain a better understanding of the cor-relations in question. Ultimately, our efforts resulted in strategic changes that had a positive influence on employee turnover rates.”

Question : 6. Which non-technical skills do you find most valuable in your role as a data engineer?

How to Answer
Although technical skills are of major importance if you want to advance your data engineer career, there are many non-engineering skills that could aid your success. In your answer, try to avoid the most obvious examples, such as communication or inter-personal skills.

Answer Example
“I’d say the most useful skills I’ve developed over the years are multitasking and prioritizing. As a data engineer, I have to prioritize or balance between various tasks daily. I work with many departments in the company, so I receive tons of different requests from my coworkers. To cope with those efficiently, I need to put fulfilling the most urgent company needs first without neglecting all the other requests. And strengthening the skills I mentioned has really helped me out.”

Question: 1. You have the following situation:You have eight balls of the same size. Seven of them weigh the same, and one of them weighs slightly more. How can you find the ball that is heavier by using a balance and only two attempts at weighing?

You can put six of the balls on the balance. If one of the sides is heavier you will know that the heavier ball is on that side. If not, the heavier ball is among the two that you did not measure and it will be really easy to determine precisely which ball is heavier with your second weighing.After you determine which side is heavier, you will be left with 3 balls to choose from. You have another attempt at weighing left. You can put two of the balls on the balance and see if one of them is heavier. If
it is, then you have found the heavier ball. If it is not, then the third ball is the one that is heavier.

Question : 2. You have the following situation:A windowless room has three light bulbs. You are outside the room with 3 switches, each of them controlling one of the light bulbs.

If you were told that you can enter the room only once, how are you going to tell which switch controls which light bulb?

You have to be creative in order to solve this one. You switch on two of the light bulbs and then wait for 30 minutes. Then you switch off one of them and enter the room. You will know which switch controls the light bulb that is on. Here is the tough part. How are you going to be able to determine which switch cor-responds to the other two light bulbs? You will have to touch them. Yes. That’s right. Touch them and feel, which one of them is heated. That will be the other bulb that you had turned on for 30 minutes.You will be in serious trouble if the interview-er says that the light bulbs are LED (given that they
don’t emit heat).