Data Engineer Interview Process

Data engineering is an in-demand role at tech companies. It involves in-depth application of programming, analytical, and data management skills. Several big tech companies, including FAANG, hire data engineers to leverage raw data and optimally strategize their consumer operations. 

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Data engineer interviews at FAANG and tier-1 companies are significantly challenging. You need to adopt a solid prep strategy in order to get past the stiff competition and crack these interviews. The right guidance goes a long way in influencing success in these interviews, where acceptance rates are as low as under 2%. As such, cracking data engineering interviews in 2021 is almost as difficult as cracking coding interviews. With the right prep strategy, however, it is definitely possible to beat the competition and land an offer. 

In this article, we’ll look at the Data Engineer interview process at FAANG and tier-1 companies. Most big companies have a streamlined process that tests engineers on multiple fronts, including programming, SQL, data modeling, and behavioral conduct. 

This article will cover everything you need to know about data engineering interviews in 2021: 

• Data Engineering Interview — Process and Timeline
• Coding Questions Asked at Data Engineer Interviews
• SQL Questions Asked at Data Engineer Interviews
• Data Modeling Questions Asked at Data Engineer Interviews
• Behavioral Questions Asked at Data Engineer Interviews

Data Engineering Interview — Process and Timeline

The interview process for data engineers primarily comprises three main stages:

1. The Initial HR Screen: A recruiter from Human Resources will get in touch with you. You’ll be asked basic questions around your experience, interest in the role, and specific skill sets you possess to satisfy the requirements of the role. 
   

2. The Technical Phone Screen: You’ll be asked a couple of behavioral questions and a coding question to test your approach to problem-solving. The coding question will predominantly be around data structures, mostly pertaining to arrays, trees, sorting, or linked lists. You’ll first need to brute-force the solution, following which you’ll have to write a code in a shared document. If you get past the technical phone screen round, you’re invited to the on-site interview. 
   

3. The On-site Interview: The on-site has three to four rounds, and interviews happen over the course of one full day. The rounds include:

1. The coding round
2. The SQL round
3. Data modeling round
4. Behavioral round
   

Each of these rounds can last 20-30 minutes. Your ability to solve complex, challenging problems by thinking analytically is extensively tested during the on-site interview. 

Coding interview Questions Asked at Data Engineer Interviews

Coding is an important skill that interviewers evaluate at data engineer interviews. In order to get interview-ready, make sure to practice a whole bunch of problems on the following topics:

• Arrays, strings, and linked lists
• Sorting algorithms — quicksort, merge sort, heap sort, etc.
• Hash tables and queues
• Recursion
• Trees and graphs
• Graph algorithms, including greedy algorithms
• Dynamic programming

Arrays, Trees and Linked Lists usually make up for the majority of questions asked at coding interviews for data engineers. 

Here are some problem questions that are often asked at coding interviews:

1. Given an integer n, find all the possible ways to position n queens on an n×n chessboard so that no two queens attack each other. A queen in chess can move horizontally, vertically, or diagonally.Solve the problem using recursion first even if you see some non-recursive approaches. (Click here for solution)
2. Given an array of numbers nums of size n, find an array of numbers products of size n, such that products[i] is the product of all numbers nums[j], where j!= i. (Click here for solution)
3. Given a string s containing a set of words, transform it such that the words appear in the reverse order. Words in s are separated by one or more spaces. (Click here for solution)
4. You are given an array of integers, arr, of size n, which is analogous to a continuous stream of integers input. Your task is to find K largest elements from a given stream of numbers. (Click here for solution)
5. Given a sequence, return its next lexicographically greater permutation. If such a permutation does not exist then return it in ascending order. (Click here for solution)

Go to the Interview Kickstart Problems Page to get access to more problems with solutions!

Behavioral Questions Asked at Data Engineer Interviews

Behavioral interviews are an integral part of the hiring process at big tech companies. Here are the type of questions you can expect in the interview:

1. Tell us about a time when you handled a difficult project that required you to learn multiple things and execute them.
2. Tell us about a time when you had a disagreement with your immediate manager.
3. Tell us about a time when a colleague was uncooperative. How did you deal with the situation?
4. Tell us about a time when you had to adapt to new processes in your previous organization?
5. What are your thoughts on maintaining an ideal work-life balance?
6. How do you ensure to avoid burnout when working on challenging projects?
7. Have you managed a team in the past? What have been your biggest challenges?
8. Tell us about a time when you had to take a different direction for an ongoing project?
9. How do you maintain healthy relationships at your workplace?
10. What do you do if you’re overburdened with work?
11. Tell us about a time when a coworker was deviating from ethical workplace conduct? What did you do?
12. What have been your biggest learnings as a data engineer?
    

Recommended Reading: Behavioral Interview Questions for Software Developers

Questions on Data Modeling Asked at Data Engineer Interviews

Questions on data modeling are pretty basic at data engineer interviews. They can be more complex for senior roles. Here are some questions you can expect:

1. How would you design a database for a data-heavy mobile application?
2. How would you address the security requirements of a relational database?
3. How would you increase the storage capacity for a mobile application that allows people to hail cab rides?
4. You’re given a segment of data for which you have to design a table schema so that a data scientist can process the information through queries. 
5. How would you envision the design for a mobile gaming application?

SQL Interview Questions Asked at Data Engineer Interviews

1. What is the difference between Partition and INDEX
2. If you have two ETL jobs that feed into a production table every day, do you think any problems could emerge in this setup?
3. You’re given a table with user_ids and dates on which they visited a certain platform. Find out the top 100 visitors using SQL until yesterday.
4. You’re given two tables - one which reflects the number of messages sent by Facebook, and another that reflects the number of users who responded to the message. Write an SQL query to calculate the confirmation percentage in this case. 
5. You’re given a table with complaint tickets covering different types of complaints. Write an SQL query to find the number of tickets under each type, and the number of processed tickets under each category. 
6. You’re given a table with a million rows. Tell us how you’d add a column from the original data source without impacting the user experience?
7. Say you have a table that represents the salaries of employees in a company. The table represents the annual salaries of employees from different departments, with bonuses and variable compensation packages. Write an SQL query to derive the monthly salary of a particular employee and whether or not the employee must receive his/her variable compensation for the given month. 
8. Explain the process of designing a database for a Fastfood restaurant.
9. Create a Schema table to represent the client click rate for a given digital campaign. 
10. You’re given a dataset schema that contains information of different buyers on an ecommerce site. Write an SQL query to compute the total sales of a given product on a given day. 

Recommended Reading: Facebook Data Engineer Interview Questions

Gear Up for Your Next Data Engineer Interview

If you’re looking for the ideal resource to help you nail data engineer interviews at top tech companies, enrol for Interview Kickstart’s Data Engineering Interview Masterclass to get the right guidance, direction, and prep strategy needed to crack these interviews. 

This is the only interview prep program that is tailored to help data engineers nail tech interviews. Our instructors are active hiring managers and technical leads at FAANG and tier-1 companies.

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