Top 30 Data Engineer Interview Questions & Answers


Interviews are often the most intimidating process to acquire a job. Hence, preparing for it becomes even more critical, whether you're a novice in the field of big data and want to break into a Data Engineering career or you're an experienced Data Engineer looking for career progression or transition. Given the current state of the market, you should be well-prepared for your interview. The following are some of the most common data engineer interview questions, as well as possible reasons verifying why these questions are asked and the relevant and accurate data science interview answers that you as a candidate must be well-versed with. 

Most Common Field-Related Data Engineer Interview Questions

  1. Explain data engineering?

This may seem like a simple question, but it could come up during your interview regardless of your skill level. Your interviewer wants to know what you mean when you say "data engineering," which shows that you understand what the job entails. 

So, what exactly is it? Data engineering, in the nutshell, is the technique of converting, cleaning, profiling, and integrating huge data sets. You can even go a step further and talk about what a data engineer does on a daily basis, such as creating and extracting ad-hoc data queries, managing an organization's data stewardship, and so on.

  1. Differentiate Data Warehouse from Operational Database?

This question may be intended for intermediates, but it might also be deemed an entry-level question in some situations. Your answer must be - databases that use Delete SQL commands, Insert, and Update are standard operational databases that prioritize speed and efficiency. As a result, data analysis could be a little more difficult. A data warehouse, on the other hand, focuses on accumulations, calculations, and select statements. As a result, data warehouses are an excellent option for data analysis.

  1. Explain what are the tasks of *args and **kwargs?

You should be prepared to answer complicated coding questions if you're interviewing for a more advanced position. This particular coding question is frequently asked in data engineering interviews, and you should respond by explaining to your interviewer that *args specifies an ordered function and **kwargs represents the unordered parameters utilized in a function. Writing down this code in the visual demonstration is one ideal way to exhibit your skills to your interviewer.

  1. Can you name the most important data engineering frameworks and applications?

This question is frequently given to see whether you comprehend the position's vital needs and possess the necessary technical abilities. Mention the names of frameworks, as well as your level of experience with each, in your response.

You can mention all of the technology programs you're proficient in, such as Python,  SQL, Hadoop, and more. You can also mention which frameworks you'd like to learn more about if given the chance.

  1. Can you distinguish a Data Engineer from a Data Scientist?

The recruiter is attempting to test your comprehension of various job functions within a data warehouse team with this question. Although the talents and responsibilities of these roles frequently overlap, they are distinct.

Data engineers create, test, and maintain the entire data creation system, whereas data scientists analyze and understand complicated data. They usually concentrate on Big Data organization and translation. Data scientists need data engineers to build the infrastructure on which they can work.

  1. What do you think a data engineer's everyday responsibilities are?

This quiz tests your knowledge of the position and job description of a data engineer.

You can describe some key responsibilities of a data engineer, such as:

  • Architecture development, testing, and maintenance.
  • Aligning the design with the needs of the company.
  • Data collection and data set development methods
  • Using statistics and machine learning models
  • Creating pipelines for various ETL and data transformation processes
  • Improving data de-duplication and building by simplifying data purification.
  • Finding strategies to increase data quality, flexibility, reliability, and accuracy.
  1. Can you explain the different types of Data Modelling design Schemas

In data modeling, there are primarily two types of schemas: 1) Snowflake schema and 2) Star schema

The snowflake schema is the centralized fact table that is linked to many dimensions in this case. Dimensions are present in a normalized form in numerous related tables in the snowflake schema. When the dimensions of a star schema are comprehensive and highly structured, with numerous degrees of relationship, and the child tables have numerous parent tables, the snowflake structure emerges. The snowflake effect affects only the dimensional table while the fact tables remain unaffected. 

The star schema is the most basic and straightforward of the data mart schema. This schema is commonly used to create a data warehouse and dimensional data marts. It has one or more fact tables that index a limitless number of dimensional tables. The snowflake schema is dependent on the star schema and is incapable of existing in its absence.

  1. Explain what is Data Modelling.

Data modeling is a scientific method of describing complicated data systems using a diagram to provide a pictorial and conceptual representation. You could also talk about any previous data modeling experience you've got.

  1. Define Big data and explain its linkage to Hadoop.

Big Data is a phenomenon that has arisen as a result of exponential increases in data availability, storage technology, and processing capacity, whereas Hadoop is a framework that aids in the handling of massive amounts of data found in the Big Data ecosystem. You may describe the Hadoop components as follows.

  • MapReduce 
  • Hadoop Common 
  • YARN (Yet Another Resource Negotiator)
  1. Explain the process of validating data migration from one database to another.

A data engineer's top responsibility should be to ensure that data is accurate and that no data is lost. Hiring managers ask this inquiry to learn more about your thought process for data validation.

In various instances, you should be able to discuss acceptable validation types. Validation, for example, could be as simple as a comparison or it could occur after the entire data migration.

  1. Explain NameNode. What happens in the case of NameNode failing to terminate?

It is the Hadoop Distributed File System's (HDFS) centerpiece or central node, however, it does not hold actual data. Metadata is saved. For example, the information saved in DataNodes is stored on which rack and which DataNode. It keeps track of the many files that are present in clusters. Because there is usually only one NameNode, the system may be unavailable if it crashes.

  1. Explain Block and Block Scanner in HDFS?

You should explain that Blocks are the smallest unit of a data file in your response. Hadoop divides large data files into units automatically for secure storage. The Block Scanner checks the list of blocks on a DataNode.

  1. Explain the succeeding step when a faulty data block is discovered by Block Scanner.

It's one of the most common and popular data engineer interview questions. You should respond by listing all steps taken by a Block scanner when it discovers a damaged data block.

First, DataNode informs NameNode about the faulty block.

Using an existing model, NameNode creates a replica. NameNode makes replicas based on the replication factor if the system does not destroy the faulty data block.

  1. What messages does NameNode receive from DataNode?

DataNodes provide messages or signals to NameNodes with information about the data.

The following are the two indicators:

The list of data blocks stored on DataNode and their functionality are represented by block report signals.

The DataNode's heartbeat indicates that it is alive and well. It's a recurring report that determines whether or not to use NameNode. If this signal is not sent, DataNode is no longer operational.

  1. How do you go about implementing a big data solution?

The recruiter is curious about the procedures you would take to deploy a big data solution while asking this inquiry. You should respond by focusing on the three most important steps:

  • Data Integration/Ingestion: In this process, data is extracted from data sources such as RDBMS, Salesforce, SAP, and MySQL.
  • Data Storing: The extracted data would be saved in an HDFS or NoSQL database.
  • Data processing: Finally, the solution should be deployed using processing frameworks such as MapReduce, Pig, and Spark.
  1. For Processing data efficiently what are the Python libraries that you would employ?

This question allows the hiring manager to assess whether the candidate understands the fundamentals of Python, which is the most commonly used language among data engineers.

NumPy, which is essential for efficient array processing, and pandas, which is good for statistics and data preparation for machine learning, should both be included in your solution. The interviewer may inquire as to why you would utilize these libraries and provide examples of when you would not.

  1. Can you distinguish between lists and tuples?

This question tests your in-depth understanding of Python once more. List and Tuple are data structure classes in Python. Lists are changeable and can be altered, whereas Tuples are immutable and cannot be modified. Use examples to back up your assertions.

  1. Explain about handling duplicate data points in an SQL Query.

This question can be used by interviewers to assess your SQL expertise as well as your commitment to the interview process, as they will expect you to ask questions in return. You might inquire about the type of data they work with and what values are likely to be duplicated.

To reduce duplicate data points, you could consider using the SQL keywords DISTINCT & UNIQUE. You should also provide alternate methods for dealing with duplicate data points, such as utilizing GROUP BY.

Career and Experience Related Data Engineer Interview Questions

  1. Do you have any expertise with the Hadoop framework for creating data systems?

If you have Hadoop experience, provide a full description of the job you conducted to highlight your abilities and tool expertise. You can describe all of Hadoop's major features. You might explain that you used the Hadoop framework because of its scalability and capacity to boost data processing speed while maintaining quality.

Hadoop has the following features:

It's written in Java. As a result, team members may not require any additional training. It is also simple to use.

Because the data is kept within Hadoop, it is available via various channels in the event of hardware failure, making it the greatest choice for handling huge data.

Data is kept in a cluster in Hadoop, which makes it independent of all other operations.

Learn the relevant knowledge about the tool's properties and attributes if you have no prior familiarity with it.

  1. Have you ever worked with ETL before? If you answered yes, please explain which one you like and why.

The recruiter wants to know your knowledge and experience with ETL (Extract Transform Load) technologies and processes with this question. List all of the tools in which you have experience and choose your favorite. Highlight the key features that distinguish that tool and justify your choice to establish your knowledge of the ETL process.

  1. Have you ever attempted to convert unstructured data to structured data?

It's a crucial question because the response demonstrates your knowledge of data kinds as well as your practical working experience. You can answer this question by separating the two categories briefly. For proper data analysis, unstructured data must be turned into structured data, and you can discuss the transformation methods. You must describe a real-life scenario in which you transformed unstructured data into structured data. Discuss facts pertaining to your academic projects if you are a recent graduate with no professional experience.

  1. How would you develop a new analytical product as a Data Engineer?

The hiring managers are interested in learning about your position as a data engineer in the creation of a new product and assessing your knowledge of the product development cycle. As a data engineer, you have complete control over the end output because you are in charge of creating algorithms or measurements based on accurate data.

The first stage is to study the overall product outline in order to fully know the needs and scope. The next step would be to investigate the specifics and explanations for each measure. Consider as many concerns as possible to help you build a more robust system with the appropriate level of granularity.

  1. Are you familiar with scripting languages such as Python, Java, Bash, or others?

This issue is posed to stress the necessity of scripting languages in the role of a data engineer. It is critical to have a thorough understanding of scripting languages because it helps you to rapidly perform analytical operations and automate data flow.

  1. What are the requirements for becoming a data engineer?

Every organization defines a data engineer differently, and they match your talents and certifications to the company's assessment.

If you want to be a good data engineer, you'll need the following abilities and qualifications:

  • Comprehensive understanding of data modeling.
  • Understanding database design and database architecture is essential. SQL and NoSQL database knowledge in depth.
  • Working knowledge of data stores and distributed systems such as Hadoop is required (HDFS).
  • Skills in Data Visualization
  • Data warehousing and ETL (Extract Transform Load) tools knowledge.
  • You must have strong computing and math abilities.
  • Excellent communication, leadership, critical thinking, and problem-solving skills are all pluses.

You can give concrete examples of how a data engineer would use their skills.

  1. Tell us about your recent project and the algorithm you use?

The interviewer may ask you to choose an algorithm from a previous project and may follow up with questions such as:

  • Why did you choose this algorithm, and how does it compare to others like it?
  • What is the algorithm's scalability with more data?
  • Are you pleased with the outcome? If you had more time what better action would you have implemented? 

These questions show your cognitive process as well as your technical understanding. First, decide which project you'd want to discuss. If you have a real-life example in your field and an algorithm that relates to the company's job, utilize it to pique the hiring manager's attention. Second, make a list of all the models you used and the analysis you performed. Start with small models and don't get too carried away. The recruiting managers expect you to explain the outcomes and their significance.

  1. Tell us about the tools you used in a recent project.

Interviewers aim to evaluate your decision-making abilities and tool knowledge. Take this opportunity to demonstrate the objective of choosing certain tools over others in your project. 

Explain your thought process to the hiring managers, including why you're evaluating this tool, its advantages, and the disadvantages of competing technologies. If the company uses approaches comparable to those you've previously worked on, weave your experience into the similarities.

  1. What obstacles did you face during your most recent project, and how did you overcome them?

Any company is interested in seeing how you behave in difficult situations and what you do to confront and overcome them.

When discussing the issues you encountered, use the STAR approach to frame your response:

Situation: Inform them of the conditions that led to the dilemma.

It is critical to elaborate on your participation in resolving the issue. If you took on a leadership role and came up with a viable solution, displaying it at an interview for a leadership post could be crucial.

Action: Walk the interviewer through the measures you took to resolve the issue.

Result: always explain your actions' repercussions. Discuss what you and related stakeholders have learned and discovered.

  1. Have you ever used cloud computing to work with huge data?

The majority of businesses are now shifting their services to the cloud. As a result, hiring managers want to know about your cloud computing skills, industry understanding, and outlook on the company's data.

You must respond that you are prepared to work in a virtual workspace because it offers numerous benefits, including:

  • Flexibility in scaling up the environment as needed
  • Secure data access from anywhere
  • Having backups in the event of a disaster
  1. What role can data analytics play in helping a company expand and increase revenue?

It all boils down to revenue-generating and corporate growth, and Big Data analysis has become critical for enterprises. All businesses want to hire people who can help them grow, fulfill their objectives, and increase their return on investment.

You can respond to this question by demonstrating how data analytics can help you increase sales, and improve customer satisfaction, and profit. Data analytics aids in the development of realistic goals and decision-making. Businesses may see a 5-20% increase in revenue as a result of utilizing Big Data analytics. Walmart, Facebook, and LinkedIn are just a few of the businesses that have benefited from big data analytics.

  1. Why did you pursue Data Engineering as a career path?

This question may be asked by an interviewer to understand more about your motivation and interest in pursuing a career in data engineering. They want to hire people who are enthusiastic about the field. You can begin by telling your narrative and highlighting the aspects of data engineering that excite you the most.

Those are the top Data engineer interview questions and accurate explanations on how and why such questions may be put towards you during your interview. The Data Engineer Interview answers we have accurately put forward should help you in preparing for your interview and getting through this most intimidating step in acquiring a data engineering position. 

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