Data Warehousing Interview Questions

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

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Tell me about your experience with AWS data services more broadly. Have you worked with Athena, and how do you decide when to use Athena versus Redshift for querying?🟡 Medium · Conceptual · Asked 29×How do you optimize performance in Snowflake?🟡 Medium · Conceptual · Asked 25×What are the features in Snowflake? How do you implement CDC in Snowflake?🟡 Medium · Conceptual · Asked 22×Which is SCD type 2. What is its behavior?🟢 Easy · Conceptual · Asked 10×How can you find records that are not present in the first table when you have an incremental table with the same structure?🟡 Medium · Conceptual · Asked 1×I was working in production and had to deploy into a partitioned table with 800 partitions, adding a new partition daily. The table is huge. I need to take a backup of the stable data. How would I do that using INSERT OVERWRITE into a copy table?🟡 Medium · Conceptual · Asked 1×What are the different partitioning technologies?🟢 Easy · Conceptual · Asked 1×What are the benefits of using a partitioned table?🟢 Easy · Conceptual · Asked 1×You have a source table with 1 billion records. You don't want to reload everything every day. How would you design an incremental load strategy?🟡 Medium · System Design · Asked 1×Do you know about fact tables and dimension tables? Can you please explain the difference between them?🟡 Medium · Conceptual · Asked 1×What is the difference between a fact table and a dimension table?🟡 Medium · Conceptual · Asked 1×Do you know about rectangular dimension tables?🟡 Medium · Conceptual · Asked 1×Can you explain data errors in data warehousing, and describe the difference between OLTP and OLAP systems?🟡 Medium · Conceptual · Asked 1×List all the columns that are required for managing or maintaining an incremental data load.🟡 Medium · Conceptual · Asked 1×You have an RDS instance. How would you capture all changes happening in the RDS and maintain an ACID‑compliant table in Redshift, using a virtual fast layer in S3, and then produce reporting‑level data in Redshift?🔴 Hard · Conceptual · Asked 1×If a downstream analyst says a dashboard is slow because a query over your Redshift or a thinner layer is scanning far too much data, how would you diagnose and optimize that end‑to‑end?🟡 Medium · Conceptual · Asked 1×We have to implement a Slowly Changing Dimension Type 2 in Snowflake.🟡 Medium · Conceptual · Asked 1×When would you use Snowflake, Redshift, and tasks?🟡 Medium · Conceptual · Asked 1×What other ETL tools have you worked with, such as Oracle Materialized Views or Data Vault?🟡 Medium · Conceptual · Asked 1×What about Snowflake? Have you experienced Snowflake as well?🟢 Easy · Conceptual · Asked 1×How does Snowflake support storing semi‑structured data in different ways?🟡 Medium · Conceptual · Asked 1×Tell me about the different types of Slowly Changing Dimensions.🟡 Medium · Conceptual · Asked 1×What is the difference between a schema‑on‑write and a schema‑on‑read approach in data warehousing, and can you give an example of when you would use each?🟢 Easy · Conceptual · Asked 1×Why was Amazon Redshift used? Could other services like AWS Glue be used instead?🟡 Medium · Conceptual · Asked 1×What is the difference between a star schema and a snowflake schema? Do you use them?🟡 Medium · Conceptual · Asked 1×Data is stored as facts and dimensions. What are fact and dimension tables?🟢 Easy · Conceptual · Asked 1×Differentiate between SCD type 1 and type 2: when a new record comes, do we keep track of the old record?🟡 Medium · Conceptual · Asked 1×In SCD type 2, what do we do?🟢 Easy · Conceptual · Asked 1×What is the difference between SCD1 and SCD2?🟢 Easy · Conceptual · Asked 1×What is SCD? What are the types of SCD?🟢 Easy · Conceptual · Asked 1×Explain slowly changing dimensions types 1, 2, and 3.🟡 Medium · Conceptual · Asked 1×Do you handle incremental data loading instead of full data loads?🟡 Medium · Conceptual · Asked 1×Will you explain the architecture of the Enterprise ETL pipeline you have designed?🟡 Medium · Conceptual · Asked 1×What file formats does Amazon Athena support?🟢 Easy · Conceptual · Asked 1×Shubhi, the question is simple: When a modeler is giving a proposal to someone, should they structure the table and approach with technical rationale? Which platform are you using? In Databricks, if you are giving someone a model that works on finance data and the requirement is to maintain history, from an implementation point of view, what is the underlying architecture of Databricks?🟡 Medium · Conceptual · Asked 1×Are you comfortable implementing Snowflake and Databricks with a similar model? Why would you need SCD Type 2 when implementing? Both cannot make sense if you’re leveraging either Delta Lake or Iceberg. What is the rationale to use SCD Type 2?🟡 Medium · Conceptual · Asked 1×Fair enough. Which levels of Slowly Changing Dimensions do you use?🟢 Easy · Conceptual · Asked 1×How would you implement logic for three ordered tiers (Bronze, Silver, Gold) in a target table?🟡 Medium · Conceptual · Asked 1×Explain how to implement Change Data Capture type 2 using effective start time, end time, and current flag fields. The current flag indicates whether a record is active; the start time indicates when it became active, and the end time indicates when it became inactive. These fields are required. How would you implement this in software?🟡 Medium · Conceptual · Asked 1×In a scenario where you need to build a type 2 dimension table in Snowflake, assume you have a product table (or a sales table). How would you read and implement a type 2 table, including handling target dimension, fact table, and audit files?🟡 Medium · Conceptual · Asked 1×Can you tell the difference between a full load and an incremental load?🟡 Medium · Conceptual · Asked 1×Do Snowflake warehouses use indexes?🟢 Easy · Conceptual · Asked 1×Is it possible for the reporting team to query DynamoDB directly for dashboarding, or should we use Snowflake?🟡 Medium · Conceptual · Asked 1×I have used Snowflake extensively. What is the difference between Snowflake and DynamoDB? Why did you use Snowflake and for what purpose?🟡 Medium · Conceptual · Asked 1×Why do we use data partitioning? For example, when moving data into a data warehouse using Kafka, how does partitioning help?🟡 Medium · Conceptual · Asked 1×Why should you choose a star schema instead of a snowflake schema?🟡 Medium · Conceptual · Asked 1×Provide code for SCD Type 2.🟡 Medium · Coding · Asked 1×Have you worked on Redshift? For example, an audit table with certain fields.🟢 Easy · Conceptual · Asked 1×What is the time travel feature?🟢 Easy · Conceptual · Asked 1×What are some challenges you have encountered when storing data in Amazon Redshift?🟡 Medium · Conceptual · Asked 1×Did you face any issues or challenges with Redshift? Please share.🟡 Medium · Behavioral · Asked 1×Have you worked with Athena? Do you have experience creating tables in Athena?🟢 Easy · Conceptual · Asked 1×

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