Inside the Walmart Data Engineer Interview: A Comprehensive Guide

As the world’s largest company by revenue, Walmart is a dream destination for many aspiring data engineers. With its vast data landscape and cutting-edge technologies, landing a data engineer role at Walmart can be a significant career milestone. However, the interview process is rigorous and demands a deep understanding of various data engineering concepts and technologies.

In this article, we’ll dive into the Walmart data engineer interview experience, covering the types of questions you can expect and providing valuable insights to help you prepare effectively. We’ll leverage the experiences shared by Nishchay Agrawal, a Senior Data Engineer at Walmart, who has graciously shared his interview journey.

The Walmart Data Engineer Interview Process

According to Nishchay’s experience, the Walmart Global Tech interview process for the Data Engineer role consists of five rounds before the final decision is made:

Preliminary Round (Screening Round): This round typically involves a detailed explanation of your previous projects, experience with tools like Kafka, ETL concepts, Spark, and data modeling.
Technical Interview 1 (Coding & DSA Round): This round lasts approximately 1.5 hours and focuses on medium-level data structure and algorithm questions, hard-level SQL queries, Python coding, big data concepts (Spark, Kubernetes, Airflow), cloud computing, and software development life cycle (SDLC) methodologies.
Technical Interview 2 (Data Modeling/System Design with Big Data Concepts): In this round, which can last up to 1 hour and 45 minutes, you’ll be expected to design systems like Mixpanel (an event-driven system) and answer questions related to load balancing, request handling, API development, Spark coding, optimization techniques, and advanced Java concepts.
Techno-Managerial Interview (Managerial Round): This round focuses on data modeling, ETL design, batch and stream processing, cost optimization strategies, Spark monitoring, and project management using Agile methodologies.
Director Round (Behavioral & Technical Round): In this final round, you’ll face questions from the Director of Walmart, covering your previous projects, research papers, core values, team management, leadership qualities, and technical concepts like Presto vs. Spark, Databricks, AWS, and Delta Lakes.
HR Round (General Discussion & Salary Discussion): This round involves general discussions about your experience, hobbies, strengths, weaknesses, and salary expectations.

Walmart Data Engineer Interview Questions and Answers

Based on Nishchay’s experience, here are some of the commonly asked questions during the Walmart data engineer interview process:

Data Structures and Algorithms

Find the minimum number of coins that make a change.
Given a linked list and a value x, partition the linked list around x, such that all nodes less than x come before all nodes greater than or equal to x.

SQL Questions

Write a SQL query to find managers with at least five direct reports.
Find the nth highest salary for each department using window functions or without using window functions.
Write a SQL query to find the employee with the highest salary in each department using the DENSE_RANK window function.

Spark and Big Data Concepts

How does Airflow work with Kubernetes, including pod concepts, scheduler, and worker machines?
Explain the difference between container deployment and stateful deployment in Kubernetes, and how Kubernetes manages fault tolerance.
How would you troubleshoot performance bottlenecks in a long-running Spark job?
How would you allocate resources and configure a Spark cluster with limited resources for optimal performance?
Write Python code to upload Parquet files to an S3 bucket using the boto3 library.
Explain how Airflow stores logs in S3 and the role of the Airflow backend database.

System Design and Architecture

Design the Mixpanel system (an event-driven system) and explain how load balancers, request handling, and DNS resolution work.
Write a custom API using Spring Boot, including service and controller classes.
Explain Spark optimization techniques like skewed join, broadcast join, and cost-based optimization (CBO).
Discuss the concepts of repartition vs. coalesce in Spark.
Describe Spark’s Tungsten and Catalyst optimizers.

Java and Advanced Java Concepts

Write Java code to run garbage collection using the GC collector thread.
Explain multithreading and write code for synchronization using synchronized threads.
Discuss serialization vs. deserialization and the use case of the transient keyword in Java.
Complete a Semaphore code implementation for synchronization.

ETL, Data Warehousing, and Data Governance

Explain the difference between Snowflake and Star schemas.
Describe the process of designing a data warehouse from scratch.
Discuss normalization concepts and the SCD-2 (Slowly Changing Dimension Type 2) type with examples.
Explain how to onboard a Delta Lake catalog to Presto.
Discuss Agile methodologies, including Scrum frameworks, sprints, and Jira boards.

General and Behavioral Questions

Why do you want to work at Walmart?
Describe a time when you faced a challenging situation at work and how you handled it.
What is your inspiration for joining Walmart?
Why should we hire you?
Explain your research papers or publications (if applicable).
Discuss your hobbies, strengths, and weaknesses.

While this list is not exhaustive, it provides a comprehensive overview of the types of questions you can expect during the Walmart data engineer interview process. It’s essential to prepare thoroughly by practicing coding, SQL queries, system design, and conceptual understanding of various data engineering tools and technologies.

Preparation Tips for the Walmart Data Engineer Interview

To increase your chances of success in the Walmart data engineer interview, consider the following preparation tips:

Strengthen your Data Structures and Algorithms skills: Practice DSA questions regularly, focusing on common problems like linked lists, arrays, and trees.
Enhance your SQL proficiency: Familiarize yourself with advanced SQL concepts, window functions, and query optimization techniques.
Master big data technologies: Gain in-depth knowledge of tools like Spark, Hadoop, Kafka, Airflow, and Kubernetes, as well as cloud computing services like AWS, Azure, or GCP.
Brush up on system design principles: Understand system design concepts, including load balancing, scalability, fault tolerance, and distributed systems.
Practice coding: Be prepared to write code in languages like Python, Java, or Scala, and practice implementing algorithms, data structures, and API development.
Understand data modeling and ETL processes: Familiarize yourself with data modeling techniques, ETL processes, and data warehousing concepts.
Prepare for behavioral and leadership questions: Reflect on your previous experiences, challenges, and achievements, and be ready to showcase your leadership qualities and problem-solving abilities.

Remember, the Walmart data engineer interview process is comprehensive and demanding, but with dedication and thorough preparation, you can increase your chances of landing your dream job.

Good luck with your Walmart data engineer interview!

walmart interview questions and answers | Data Engineering

FAQ

How do I prepare for a data engineer interview?

To prepare for your interview, you may find confidence in reviewing everything you’ve learned from previous roles and courses you’ve taken. Imagine yourself in the interview, whether it is in person or over Zoom, with the hiring manager asking you technical questions. Study and master SQL.

Is Walmart interview tough?

Is it hard to get hired at Walmart? Glassdoor users rated their interview experience at Walmart as 47.6% positive with a difficulty rating score of 2.91 out of 5 (where 5 is the highest level of difficulty).