Snowflake Interview Questions and Answers

1. Explain the architecture of Snowflake.

Snowflake is the popular cloud-based data warehousing platform to perform secure, scalable, and flexible storage, analysis, and sharing of data. It separates storage, compute, and cloud services which allow users to scale each independently. Snowflake has a three-layer architecture:

Storage layer to store data in compressed, optimized format. Compute layer uses virtual warehouses for querying and processing data. Cloud services layer manages metadata, security, and query optimization.

2. What is the significance of micro-partitions in Snowflake?

Snowflake stores data as small, immutable chunks called micro-partitions. This approach improves query performance through automatic clustering, compression, and efficient pruning of data.

3. What are virtual warehouses in Snowflake?

In snowflake, virtual warehouses are clusters of compute resources used to run queries and perform data operations. They can be scaled up or down independently and paused when not in use.

4. What makes Snowflake different from traditional data warehouses?

Snowflakes differ from traditional data warehouses by separating storage and compute for independent scaling. It is fully managed without the requirement of infrastructure management. It supports semi-structured data, automatic scaling and concurrency.

5. What are the types of caching in Snowflake?

Types of caching in snowflake

Result cache stores query results for reuse. Local disk cache stores data on compute nodes during query execution. Metadata cache stores table and schema metadata.

6. How does Snowflake handle data storage? What is a Snowflake database?

In cloud storage, Data is stored in columnar format that is optimized for compression and retrieval. Snowflake automatically manages partitioning and metadata for efficient access. Snowflake database is a logical grouping of schemas, tables, views, and other database objects.

7. How do you load data into Snowflake?

Load data into snowflake using:

COPY INTO command with external stages.
Snowpipe for continuous data loading.
Third-party ETL tools.

8. What is Snowpipe and external table in snowflake?

Snowpipe is a continuous data ingestion service that automatically loads data as new files arrive in the stage. External table refers to data stored in an external location like S3, Azure Blob without importing it into Snowflake’s internal storage.

9. What is a transient table in Snowflake?

Transient table is used to store temporary data with no fail-safe retention period. It reduces storage costs compared to permanent tables.

10. How do you create and use a schema in Snowflake?

To create schema in snowflake:

CREATE SCHEMA my_schema;

To use a schema

USE SCHEMA my_schema;

11. How do you optimize query performance in Snowflake?

To optimize query performance, use appropriate warehouse size and prune data with filters and partitions. Materialized views for precomputed results with query caching and automatic clustering.

12. How does Snowflake handle concurrency?

Snowflake supports high concurrency through its multi-cluster virtual warehouses and enables multiple users to run queries without contention.

13. What are the stages in Snowflake?

In snowflake, stages are storage locations used for loading and exporting data. Types of stage:

User stage
Table stage
Named stage

14. What is the RESULT_CACHE in Snowflake?

The Result Cache is used to store results of queries for 24 hours. If the same query is executed, Snowflake returns results from the cache.

15. What is a materialized view in Snowflake?

Materialized view is a precomputed query result which is stored for faster access. It automatically updates when the underlying data changes.

16. How does Snowflake ensure data security?

Snowflake ensures data security by encrypting data in transit (TLS) and at rest (AES-256) with role-based access control (RBAC). It uses multi-factor authentication (MFA) and network policies for IP whitelisting.

17. What is Time Travel in Snowflake? How do you use Time Travel to query historical data?

Time Travel allows you to access historical data or recover dropped objects within a specified retention period.

To query historical data using time travel:

SELECT * FROM my_table AT (TIMESTAMP => ‘2024-06-01 12:00:00’);

18. What is data masking and data sharing in Snowflake?

Data masking hides sensitive data by displaying obfuscated or anonymized versions. It protects privacy and compliance with regulations. Data sharing allows organizations to share live data with other accounts without copying or moving data.

19. How does Snowflake support auditing?

Snowflake supports auditing by providing query history and access logs to audit user activities and data access.

20. What is role-based access control (RBAC) in Snowflake?

RBAC manages user permissions through roles and granting access based on the principle of least privilege.

21. How do you create a role in Snowflake?

To create a role on snowflake

CREATE ROLE analyst;

GRANT USAGE ON DATABASE my_db TO ROLE analyst

22. How does automatic clustering work in Snowflake?

Snowflake manages data clustering automatically based on query patterns and optimizes the storage for better performance.

23. How do different types of caching work in Snowflake?

Result cache stores the results of queries for 24 hours. The results are fetched from the cache without recomputation if the same query is running.

Local Disk Cache stores data on the virtual warehouse’s local SSD during query execution and speeds up subsequent queries.

Metadata Cache stores information about the table structure and schema by speeding up query parsing and optimization.

24. What is the STREAM object in Snowflake, and how is it used?

STREAM tracks changes like inserts, updates, deletes in a table for Change Data Capture (CDC) use cases. It allows efficient identification of changes without scanning the entire table.

25. What are the different types of tables in Snowflake?

Snowflake supports three types of tables:

Permanent Table is the default table type with full fail-safe and Time Travel support.
Transient Table is for temporary data with no fail-safe and reducing storage costs.
Temporary Table exists only for the duration of a session and is not visible to other users.

Request more information

Snowflake Interview Questions and Answers