Data Engineering Interview Questions

72 real Data Engineering questions asked in live technical interviews — each with a model answer. Updated weekly.

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Can you explain briefly what technologies you have used or what kind of work you have done on a daily basis, and what kind of data or transformations you have dealt with?🟢 Easy · Behavioral · Asked 34×Can you dig deeper and explain what technologies you have used, what processes you follow, and what kind of data transformations you have dealt with on a daily basis?🟡 Medium · Behavioral · Asked 27×What do you mean when you say you are facing difficulty in collecting the data?🟡 Medium · Conceptual · Asked 14×How should I prepare for data engineering interviews?🟡 Medium · Conceptual · Asked 3×You're tasked with designing a distributed data processing system using Apache Spark and Apache Kafka that can process 10 million events per second and write the results to a data warehouse. How would you design the system and what technologies would you use?🔴 Hard · System Design · Asked 2×What does a data engineer do?🟢 Easy · Conceptual · Asked 1×What level of DSA knowledge is required for a data engineering role at companies like Microsoft, Amazon, or Paytm?🟡 Medium · Conceptual · Asked 1×Can you tell me a bit about yourself as a data engineer?🟢 Easy · Behavioral · Asked 1×Suppose you're given a dataset with 100 million rows and you need to perform a complex query that involves aggregating data from multiple tables. How would you optimize the query for better performance using Apache Spark's advanced features like GraphX and MLlib?🔴 Hard · Conceptual · Asked 1×Let's see if you think like a senior data engineer. His Spark job takes 20 minutes every day. Today it took two hours. What's the first thing you will check?🟡 Medium · Debugging · Asked 1×Let's see if you think like a senior data engineer. His Spark job takes 20 minutes every day. Today it took two hours. What is the first thing you will check? If you answer 'was', I will see the code.🟡 Medium · Debugging · Asked 1×Have you worked on streaming data?🟡 Medium · Conceptual · Asked 1×Have you used Databricks?🟢 Easy · Behavioral · Asked 1×Are you aware of any Spark optimization techniques that have been used in projects?🟡 Medium · Conceptual · Asked 1×Have you worked on PySpark or Scala?🟢 Easy · Behavioral · Asked 1×Have you worked with Databricks and Snowflake?🟡 Medium · Conceptual · Asked 1×What is the difference between repartition and coalesce in Spark, and when would you use each?🟡 Medium · Conceptual · Asked 1×How should I prepare for a data engineering interview? Should I focus on system design, and what topics should I study?🟢 Easy · Conceptual · Asked 1×Explain how repartitioning works in Spark and when it is used.🟡 Medium · Conceptual · Asked 1×Are you familiar with Databricks?🟢 Easy · Conceptual · Asked 1×Is the process manual? I want to embed the approach in an automation workflow. For time travel, we can get it. But I don't see it as viable to handle, say, 50–60 GB of data.🟡 Medium · Conceptual · Asked 1×What do you mean by automating data workflows, and what tools or technologies have you used for this purpose?🟢 Easy · Conceptual · Asked 1×Have you done any migration projects?🟡 Medium · Behavioral · Asked 1×Can you describe how you build ingestion logic and transformation, perform validation checks, leverage APIs, and trigger actions based on comparisons?🟡 Medium · Conceptual · Asked 1×Between Python and PySpark on Databricks, which is more professional? If you had to choose a primary skill set, what would you pick?🟡 Medium · Conceptual · Asked 1×In which part are you mainly focused? In the current project, what do you exactly do? Is your role extracting data or transforming data?🟡 Medium · Conceptual · Asked 1×I have some CSV files located in an S3 bucket. I want to convert all CSV files to Parquet to save cost and improve performance. What approach should I use?🟡 Medium · Conceptual · Asked 1×In data engineering projects, after developing pipelines, do we deploy them at the end?🟢 Easy · Conceptual · Asked 1×What is Glue in data engineering?🟢 Easy · Conceptual · Asked 1×Are there multiple popular ETL tools in the market such as Informatica, Talend, AWS Glue, and Azure Data Factory? Tech giants like Amazon, Google, Microsoft, IBM, and Deloitte use these ETL products to create scalable data pipelines. Can you explain the ETL process?🟡 Medium · Conceptual · Asked 1×Explain the ETL process in data engineering. What do the steps Extract, Transform, and Load entail?🟢 Easy · Conceptual · Asked 1×Can you highlight a specific project and explain a use case that uses different data engineering technologies?🟡 Medium · Behavioral · Asked 1×What is the difference between batch processing and stream processing in AWS?🟡 Medium · Conceptual · Asked 1×Where is data stored in the bronze, silver, and gold layers?🟡 Medium · Conceptual · Asked 1×Suppose we have bronze, silver, and gold layers. Where is data stored in each layer?🟡 Medium · Conceptual · Asked 1×How would you handle errors when data is corrupted while working on streaming data?🟡 Medium · Conceptual · Asked 1×What are common data pipeline issues inside Change Data Capture (CDC)?🟡 Medium · Conceptual · Asked 1×Do you have experience writing Python and SQL?🟢 Easy · Other · Asked 1×How do you manage large volumes of data in a deep learning pipeline implementation using PySpark, including partitioning and handling bursts of data?🟡 Medium · Conceptual · Asked 1×Do you have experience with both batch and stream processing?🟢 Easy · Conceptual · Asked 1×Can you explain DBT in technical language?🟡 Medium · Conceptual · Asked 1×Can you explain DBT using layman terms with an example involving mango?🟢 Easy · Conceptual · Asked 1×I want to know what data engineering is all about. I come from a non‑tech background. Please explain it in two or three brief lines.🟢 Easy · Conceptual · Asked 1×What is the difference between a normal ATL pipeline and a DLT pipeline?🟡 Medium · Conceptual · Asked 1×Why use a DLT pipeline?🟢 Easy · Conceptual · Asked 1×Did you use the auto loader option in Databricks?🟢 Easy · Behavioral · Asked 1×As a data engineer, would you choose a batch job?🟢 Easy · Conceptual · Asked 1×As a data engineer, how would you retrieve complete data?🟡 Medium · Conceptual · Asked 1×What recent technologies have been used in data pipelines?🟡 Medium · Conceptual · Asked 1×What is the difference between a normal Delta table and a Delta Live Table?🟡 Medium · Conceptual · Asked 1×Within an ETL pipeline, how do you handle error calls?🟡 Medium · Conceptual · Asked 1×If you have worked on an ETL pipeline, can you explain which critical pipeline you have designed and describe its architecture?🔴 Hard · Conceptual · Asked 1×Let me give a scenario: we have a market file in S3 and want to load the data into our cluster. How would you load it?🟡 Medium · Coding · Asked 1×Can you explain any of the recent projects you have worked on that involved water extraction?🟡 Medium · Behavioral · Asked 1×Did you manually connect a Spark job to an S3 bucket?🟡 Medium · Conceptual · Asked 1×Then tell me, did you organize market data? What file format did you use?🟡 Medium · Conceptual · Asked 1×Many of us handle incremental data loading. What was the daily data volume of yours? Did you use CDC watermarking, merge, append, or any other approach?🟡 Medium · Conceptual · Asked 1×Suppose we have some records that do not match the expected schema, containing null or invalid price values. How would you separate bad records to ensure only valid data is loaded for valuation?🟡 Medium · Conceptual · Asked 1×Suppose multiple CSV files are coming daily into an S3 bucket, and sometimes the schema changes: new columns are added or data types change. How would you handle this situation in PySpark? Explain the steps and logic behind your approach.🟡 Medium · Conceptual · Asked 1×Describe how you build an end‑to‑end data pipeline.🔴 Hard · System Design · Asked 1×Explain a complex Python PySpark code you have created in either your current or past projects. First describe the business problem, then explain the code you wrote to solve it.🟡 Medium · Behavioral · Asked 1×Is there another scenario where a data engineering team updates a 50 TB ISO table often using copy‑on‑write?🟡 Medium · Conceptual · Asked 1×What would be your thought process for designing dynamic data pipelines?🟡 Medium · Conceptual · Asked 1×Given a scenario where files are coming into an S3 bucket and need to be loaded into Redshift, but the files sometimes change their schema, how would you establish dynamic schema enforcement?🟡 Medium · Conceptual · Asked 1×Do you know about the Medallion Architecture?🟡 Medium · Conceptual · Asked 1×Vaishnavi, let's start with a brief introduction. Can you give an overview of your total professional experience? What have you worked on from a data engineering perspective? Specifically, what tech stack have you worked with?🟡 Medium · Behavioral · Asked 1×Design a data pipeline.🟡 Medium · System Design · Asked 1×Can you tell me what vacuum is in Databricks?🟡 Medium · Conceptual · Asked 1×Generally, how do you optimize an ADS pipeline if it is running long?🟡 Medium · Conceptual · Asked 1×Can you explain the difference between generic and dynamic approaches when building a pipeline?🟡 Medium · Conceptual · Asked 1×What is your experience with Airflow and data grid?🟡 Medium · Behavioral · Asked 1×Data is loading again. How do you prevent data from being duplicated if the same file is loaded multiple times? What mechanisms can you implement to delete or ignore duplicate data after it has been loaded?🟡 Medium · Conceptual · Asked 1×

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