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How To Prepare For Data Engineer Interview

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Explain The Reducer Phases And Their Core Methods

How To Prepare For A Data Engineering Interview

The Hadoop Reducer processes the data output of the mapper, and it produces the final output stored in HDFS.

The Reducer mainly has 3 phases:

  • Shuffle: Here, the output from mappers is shuffled, and it acts as the input for the Reducer.
  • Sorting is done while shuffling, and at the same time, the output from different mappers is sorted.
  • Reduce: Here, the Reduces aggregates the key-value pair and gives the output, which is then stored on HDFS and is not further sorted.
  • There core methods in Reducer:

  • Setup: This configures various parameters, such as input data size.
  • Reduce: It is defined as the main operation of the Reducer. Here, a task is defined for the associated key.
  • Cleanup: This method cleans up the temporary files at the end of the task.
  • What Happens When Block Scanner Detects A Corrupted Data Block

    It is one of the most typical and popular interview questions for data engineers. You should answer this by stating all steps followed by a Block scanner when it finds a corrupted block of data.

    Firstly, DataNode reports the corrupted block to NameNode.NameNode makes a replica using an existing model. If the system does not delete the corrupted data block, NameNode creates replicas as per the replication factor.

    Questions About Experience And Background

    The following background and experience questions help the hiring team evaluate your qualifications and assess whether your goals are in line with the organization’s values and objectives:

    • What would you bring to our organization?
    • What do you like most about your current job?
    • What do you like least about your current position?
    • Tell us about your data engineering work experience.
    • What do you appreciate most about data engineering?
    • What do you enjoy least about data engineering?
    • Can you describe your biggest accomplishment?
    • What is your preferred work environment?
    • Are you comfortable with reporting to superiors younger than you?
    • Do you consider yourself a leader?
    • What is your definition of professional success?
    • How do you envision your career path?
    • Where do you see yourself in five years?

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    Essential Data Engineering Interview Questions And Answers

    Guest Contributor

    One of the most substantial economic effects of the COVID-19 pandemic was the acceleration of workplace trends like the transition to remote work. While some businesses needed to shut their doors amid the economic slowdown, others have been growing and interviewing this whole time. Companies like GitHub, Salesforce, Oracle, and Pfizer were among the top for remote job offerings in the past year.

    If youre an aspiring data engineer, dont let the pandemic hold your career prospects back any longer. Look for remote data engineering positions at companies like these. Chances are, youll be invited for an interview . So, all that being said, how can you prepare for the data engineering interview in 2021?

    What Is Your Approach To Developing A New Analytical Product As A Data Engineer

    How to Prepare for Microsoft Software Development ...

    The hiring managers want to know your role as a data engineer in developing a new product and evaluate your understanding of the product development cycle. As a data engineer, you control the outcome of the final product as you are responsible for building algorithms or metrics with the correct data.

    Your first step would be to understand the outline of the entire product to comprehend the complete requirements and scope. Your second step would be looking into the details and reasons for each metric. Think about as many issues that could occur, and it helps you to create a more robust system with a suitable level of granularity.

    Read Also: What Are Some Questions They Ask In An Interview

    How Is Data Security Ensured In Hadoop

    Following are some of the steps involved in securing data in Hadoop:

    • You need to begin by securing the authentic channel that connects clients to the server.
    • Second, the clients make use of the stamp that is received to request a service ticket.
    • Lastly, the clients use the service ticket as a tool for authentically connecting to the corresponding server.

    7 How Would You Validate A Data Migration From One Database To Another

    The data engineer candidate should be concerned with the validity of data and ensuring that no data is dropped. They should be able to explain how validation of data would happen. In some cases, a comparison between hashes or timestamps can be used in other cases, a more thorough comparison of data is needed to be able to validate.

    The candidate should be able to give you an idea of which type of validation is appropriate in different scenarios. For example, the validation could occur continuously as the data flows into both databases, or the validation could occur once after a complete data migration happens. There could also be other approaches that the candidate suggests. The validation could also be a simple comparison, or more involved .

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    4 How Would You Deal With Duplicate Data Points In An Sql Query

    This is a good question to ask a candidate because it should get them to ask you questions in return. For instance, they should ask you what kind of data you are working with, and what columns or values would likely be duplicated.

    They should also suggest using the SQL keywords, UNIQUE and DISTINCT, for reducing duplicate data points. After that they should also suggest other ways to deal with duplicate data points, such as grouping the data using GROUP BY and filtering it further.

    If you want to know if a candidate has a good grasp of SQL, ask this question.

    Define Do *args And **kwargs

    Preparing For A Data Engineering Interview: How To Design A Data Warehouse For.A Food Delivery App

    *args and **kwargs are special keywords that allow the function to take the variable-length arguments. **kwargs are used to pass the variable number of keyword arguments dictionary to the function on which the operation of a dictionary is performed. *args and **kwargs usually make the function flexible.

    Recommended Reading: What To Ask In An Interview As A Candidate

    Questions On Design Patterns And Etl Concepts

    In large applications, youll often use more than one type of database. In fact, its possible to use PostgreSQL, MongoDB, and Redis all within just one application! One challenging problem is dealing with state changes between databases, which exposes the developer to issues of consistency. Consider the following scenario:

  • A value in Database #1 is updated.
  • That same value in Database #2 is kept the same .
  • A query is run on Database #2.
  • Now, youve got yourself an inconsistent and outdated result! The results returned from the second database wont reflect the updated value in the first one. This can happen with any two databases, but its especially common when the main database is a NoSQL database, and information is transformed into SQL for query purposes.

    Databases may have background workers to tackle such problems. These workers extract data from one database, transform it in some way, and load it into the target database. When youre converting from a NoSQL database to a SQL one, the Extract, transform, load process takes the following steps:

  • Extract: There is a MongoDB trigger whenever a record is created, updated, and so on. A callback function is called asynchronously on a separate thread.
  • Transform: Parts of the record are extracted, normalized, and put into the correct data structure to be inserted into SQL.
  • Load: The SQL database is updated in batches, or as a single record for high volume writes.
  • How To Prepare For An Azure Data Engineer Interview

    This article will cover a few key tips for acing an upcoming Azure Data Engineerinterview by empowering candidates to master the traditional Microsoft BI Stackand then understand Azure’s Modern Enterprise Data and Analytics Platform, the variousbig data options and performance tuning recommendations, along with fundamentalrequirements of the Azure Data Engineer Associate certification. Finally, we willcover the value of expanding your knowledge across other Azure specialties to addressthe business value of an Azure data solution.

    Master the traditional Microsoft Business Intelligence Stack

    There are many online resources and books to help with mastering the traditionalMicrosoft BI skillset. Read‘The Data Warehouse toolkit’ by Ralph Kimball for a thorough understanding ofdimensional modeling. There are many other online resources for learning MicrosoftBI ranging from paid courses to free YouTube tutorials.

    Understand Azure’s Modern Enterprise Data and Analytics Platform

    Finally, have a good understanding of recent trends, feature updates, availabilityreleases and more of new and existing Azure data resources.Azure Updatesis a great place to find many of these updates and you could filter the productcategories to the data engineering specific resources. There are many other freelearning resources available, ranging from articles to video tutorials on the keepingup with the latest and greatest in the Azure Data Platform.

    Understand how to manage Big Data withAzure

    Next Steps

    Also Check: How To Prepare Google Interview

    Data Engineering Interview Prep Guide

    I have been working as a data engineer for the past three years, and one thing that I have noticed is that there is a distinct lack of readily available resources for preparing for data engineering interviews. This is probably partially due to the fact that data engineering as a field is not particularly well defined the role varies from company to company and domain to domain, sometimes tracking closer with software engineering and sometimes more with data science or analytics.

    Well, never fear! The following is a brief list of the resources that I think can be most helpful for preparing for the technical round of data engineering interviews. I intend for this to be a living document that I will continue to grow and update over time, adding new resources that I come across as well as those suggested to me by others in the field. I think preparation can be broadly broken up into these categories:

  • Coding
  • Soft skills
  • What Is Block And Block Scanner In Hdfs

    How much Programming for Data Science

    Block is considered as a singular entity of data, which is the smallest factor. When Hadoop encounters a large file, it automatically slices the file into smaller chunks called blocks.

    A block scanner is put into place to verify whether the loss-of-blocks created by Hadoop is put on the DataNode successfully or not.

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    What Do You Do To Manage Your Time And Stay On Schedule And Have Your Time Management Skills Improved Since Starting Your Career

    The answer to this question should inform the interviewer you have some project management abilities. This is your opportunity to discuss how developed your time-management skills are and how you continue to improve those. Your answer should also reflect on how well you handle demanding projects.

    Example:Before I begin any work, I set aside some time to prioritize what tasks need to be done right away, and follow my list, doing the most time-sensitive parts first. Using this process has kept me on time and continues to improve my time-management skills.

    Data Challenge Was Very Similar To The Ads Analysis Challenge On The Book The Collection Of Data Science Takehome Challenge So That Was Easy Sql Was: You Have A Table Where You Have Date User: Id Song: Id And Count It Shows At The End Of Each Day How Many Times In Her History A User Has Listened To A Given Song So Count Is Cumulative Sumyou Have To Update This On A Daily Basis Based On A Second Table That Records In Real Time When A User Listens To A Given Song Basically At The End Of Each Day You Go To This Second Table And Pull A Count Of Each User/song Combination And Then Add This Count To The First Table That Has The Lifetime Count If It Is The First Time A User Has Listened To A Given Song You Won’t Have This Pair In The Lifetime Table So You Have To Create The Pair There And Then Add The Count Of The Last Day Onsite: Lots Of Ads Related And Machine Learning Questions How To Build An Ad Model How To Test It Describe A Model I Didn’t Do Well In Some Of These

    Can’t tell you the solution of the ads analysis challenge. I would recommend getting in touch with the book author though. It was really useful to prep for all these interviews.SQL is a full outer join between life time count and last day count and then sum the two.Moins

    Can you post here your solution for the ads analysis from the takehome challenge book. I also bought the book and was interested in comparing the solutions. Also can you post here how you solved the SQL question?Moins

    for the SQL, I think both should work. Outer join between lifetime count and new day count and then sum columns replacing NULLs with 0, or union all between those two, group by and then sum.Moins

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    Preparing For Your Data Engineering Interview

    When trying to land a data engineering job, you can expect the interview process to be broken into several parts:

    • Pre-screening interview to determine potential fit.
    • Technical pre-screen test to assess your skills.
    • Take home tests or a test project.
    • In-person interview.

    You can expect data engineer interview questions to focus on a few key areas, so to prepare, start by thinking of examples you can share related to:

    • Coding including data structures, algorithms and problem solving.
    • Database design such as data modeling and data warehouses.
    • Data architecture and big data technologies with programs like Hadoop, Spark, and event processing technologies like Kafka.
    • SQL projects and examples.

    Next, youll want to think about your transferable skills. These are skills not specific to the role of a data engineer, but critical skills such as communication, leadership, organization and time management.

    Some of the most common data engineer interview questions you can expect are ones where you are asked to share specific scenarios that demonstrate your skills in action. These questions often start with tell me about a time when.If you have any use cases you can reference, brushing up on these while youre prepping is a great idea. In terms of how to best answer these questions, the STAR method is designed to help you with great storytelling focusing on the situation, task, action and result.

    Questions About Engineering Experience And Background

    How I Prepared For My FAANG Interviews (As A Data Engineer)

    Your answers to questions involving your background and experience give the interviewer an idea of your qualifications for the position you applied for. During this time, you can determine if the companys values line up with yours.

    • What kind of education do you have? How much education do you have?
    • What do you like about engineering?
    • What is your least favorite thing about engineering?
    • What do you think makes a great engineer?
    • Why did you apply for this particular position? What appeals to you about our company?
    • How do you motivate a team of engineers when a project is floundering?
    • What is the biggest challenge you have ever faced as an engineer?
    • Do you have any security clearance to work on classified projects?
    • Have you ever helped save money in previous jobs? How did you save it and what was the amount that you saved?
    • What is your greatest success that youve had in engineering?
    • Do you ever lose your temper while working? If so, how do you recover?

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    What Is Data Engineering

    Interviewers frequently bring this question up to assess whether you can discuss your field in an understandable and competent way. When you answer, try to include a general summary as well as a brief discussion of how data engineers collaborate with colleagues.

    Example:âData engineering powers the collection and processing of information through a combination of desktop software, mobile applications, cloud-based servers and physical infrastructure. Effective data engineering requires careful construction, strong pipelines and smart collaborators. Data engineers are essential partners of data scientists, who analyze and use the information we collect.â

    How Can We Achieve Security In Hadoop

  • In the first step, we have to secure the authentication channel of the client to the server. You have to Provide time-stamped to the client.
  • Next, the client uses the received time-stamped to request the TGS for the service ticket.
  • Lastly, the client makes use of a service ticket for self-authentication to the specific server.
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    What Are The Sample Questions In This Book

    • What is the difference between ROLLBACK TO SAVEPOINT and RELEASE SAVEPOINT?
    • How will you see the current user logged into MySQL connection?
    • Can we create multiple tables in Hive for a data file?
    • Can we use Hive for Online Transaction Processing systems?
    • Can we use same name for a TABLE and VIEW in Hive?
    • How can we get a random number between 1 and 100 in MySQL?
    • How can you copy the structure of a table into another table without copying the data?
    • How can you find 10 employees with Odd number as Employee ID?
    • How does CONCAT function work in Hive?
    • How will you change the data type of a column in Hive?
    • How will you check if a file exists in HDFS?
    • How will you check if a table exists in MySQL?
    • How will you run Unix commands from Hive?
    • How will you search for a String in MySQL column?
    • How will you see the structure of a table in MySQL?
    • How will you select the storage level in Apache Spark?
    • How will you synchronize the changes made to a file in Distributed Cache in Hadoop?
    • If we set Replication factor 3 for a file, does it mean any computation will also take place 3 times?
    • Is it safe to use ROWID to locate a record in Oracle SQL queries?
    • What are different Persistence levels in Apache Spark?
    • What are the common Transformations in Apache Spark?

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