General Snowflake Questions
Q1: What is Snowflake, and how is it different from traditional databases?
Snowflake is a cloud-oriented data warehousing platform that distinguishes between storage and computational resources. Unlike traditional databases, Snowflake supports scalability, native support for semi-structured data (like JSON), and enables multiple concurrent workloads without performance degradation.
Q2: Explain the concept of Snowflake`s architecture.
Snowflake uses a multi-cluster shared data architecture consisting of three layers:
- Storage Layer:Data is stored in a compressed, columnar format.
- Compute Layer:Independent virtual warehouses process data.
- Cloud Services Layer: Manages metadata, security, and optimization.
Q3: What are virtual warehouses in Snowflake?
Virtual warehouses are compute clusters that perform operations like querying, loading data, and data transformations. They can be scaled independently.
Q4: What is time travel in Snowflake?
Time travel allows users to access historical data (up to a specified retention period, typically 1-90 days) to recover from accidental deletions or modifications.
Q5: What is the role of the metadata services in Snowflake?
Metadata services manage schema, query optimization, security, and transaction control, ensuring real-time access and minimal latency.
Scenario Based Questions
Q1: You accidentally deleted a table. How can you recover it in Snowflake?
Use the UNDROP TABLE command within the time travel retention period. If the retention period has passed, you can recover from Fail-safe by contacting Snowflake support.
Q2: You need to ensure different teams can query the same data simultaneously without performance degradation. How would you achieve this in Snowflake?
Create separate virtual warehouses for each team. Each warehouse will operate independently, ensuring workload isolation.
Q3: Your query performance is slow during peak hours. What can you do?
Scale up the virtual warehouse by increasing the size or scale out by adding more clusters to the multi-cluster warehouse.
Q4: How would you secure sensitive data in Snowflake?
Use Snowflake`s data masking to hide sensitive information and configure Role-Based Access Control (RBAC) to restrict access.
Q5: How would you load semi-structured data like JSON into Snowflake?
Load the data into a variant column using the COPY INTO command and parse it with built-in functions like FLATTEN.
Q1: How does Snowflake handle data compression?
Snowflake automatically compresses data in the storage layer using proprietary algorithms, improving query performance and reducing costs.
Q2: What is clustering in Snowflake?
Clustering organizes data based on specified columns to optimize query performance. Use the RECLUSTER command for manual adjustments.
Q3: When should you use a multi-cluster warehouse?
Use it when there are high concurrent workloads to balance resources dynamically across clusters.
Q4: What is the result caching mechanism in Snowflake?
Snowflake caches query results for 24 hours, reducing repeated query execution time.
Q5: How can you improve query performance?
Use partitioning, clustering, result caching, and avoid overusing joins or subqueries.
Architectural Level Questions
Q1: How does Snowflake ensure data durability and availability?
Snowflake replicates data across multiple availability zones or regions and uses storage services like Amazon S3, Azure Blob Storage, or Google Cloud Storage.
Q2: How does Snowflake achieve concurrency?
By separating compute resources (virtual warehouses), multiple users can run queries simultaneously without contention.
Q3: What makes Snowflake`s architecture cloud-native?
It leverages cloud storage, on-demand scaling, and stateless compute nodes, ensuring seamless integration with cloud providers.
Q4: What are Snowflake`s integrations with third-party tools?
Snowflake integrates with BI tools like Tableau, Power BI, and ETL tools like Talend and Informatica.
Q5: How does Snowflake handle schema changes?
Schema changes are dynamic, allowing users to add or modify columns without affecting performance.
Q1: What is the COPY command in Snowflake?
The COPY INTO command is used to load bulk data from files into Snowflake tables.
Q2: How does Snowflake support ELT workflows?
Snowflake`s native SQL engine supports in-database transformations, eliminating the need to move data.
Q3: What are file formats supported for data loading?
Snowflake supports CSV, JSON, Parquet, ORC, and Avro.
Q4: How do you handle duplicate records during data loading?
Use the ON_ERROR parameter or deduplicate records using SQL transformations.
Q5: How does Snowflake handle large datasets?
By leveraging columnar storage and horizontal scaling, Snowflake optimizes data processing and querying.
Security and Compliance Questions
Q1: What is Snowflake`s approach to data encryption?
Snowflake encrypts data at rest and in transit using AES-256 encryption.
Q2: What is Dynamic Data Masking in Snowflake?
It hides sensitive data based on user roles, ensuring only authorized users can view original data.
Q3: How does Snowflake ensure compliance?
Snowflake complies with standards like GDPR, HIPAA, and SOC 2.
Q4: What are roles in Snowflake?
Roles are used to manage permissions and access control for objects in Snowflake.
Q5: What is row-level security in Snowflake?
Row-level security applies filters based on user roles, allowing only relevant data access.
Advanced and Cloud Integration Questions
Q1: How does Snowflake integrate with AWS services?
Snowflake connects to AWS S3 for data loading and uses Amazon KMS for encryption.
Q2: What is Snowpipe?
Snowpipe is a real-time data ingestion service that automates data loading into Snowflake.
Q3: How do you use streams in Snowflake?
Streams track changes in a table for incremental processing.
Q4: What is a task in Snowflake?
Tasks automate SQL execution on a scheduled basis or based on stream activity.
Q5: What are external stages in Snowflake?
External stages define external cloud storage locations (like S3) for data loading or unloading.
Scenario Based Advanced Questions
Q1: How would you enable real-time data updates in Snowflake?
Use Snowpipe for real-time ingestion and combine it with streams and tasks for transformation.
Q2: You need to migrate a large on-premises database to Snowflake. How would you proceed?
Export data to cloud storage, use COPY INTO to load it, and validate data using checksum or record counts.
Q3: How would you monitor costs in Snowflake?
Use Account Usage and query the SNOWFLAKE.ACCOUNT_USAGE views to track compute, storage, and query costs.
Q4: How would you optimize a report with slow queries?
Analyze the execution plan, use clustering, and leverage caching for frequently accessed data.
Q5: How would you ensure high availability for critical applications?
Use multi-region replication and monitor virtual warehouses for seamless failover.
Miscellaneous Questions
Q1: What is zero-copy cloning in Snowflake?
It creates a copy of a database, schema, or table without duplicating the data, saving storage costs.
Q2: What is materialized view in Snowflake?
A materialized view stores query results for faster performance on repeated queries.
Q3: How do you unload data from Snowflake?
Use the COPY INTO command to export data to cloud storage.
Q4: What is the purpose of data sharing in Snowflake?
Data sharing allows organizations to share live, query able data without duplication.
Q5: What are Snowflake connectors?
Snowflake offers connectors for Python, Java, ODBC, and JDBC to interact with applications.
Practical Questions
Q1: How do you monitor Snowflake usage?
Use the Query History tab and INFORMATION_SCHEMA views.
Q2: What is a warehouse credit in Snowflake?
It is a billing unit representing the time a virtual warehouse spends on processing.
Q3: How do you perform data masking in Snowflake?
Define masking policies and attach them to columns during table creation.
Q4: What is fail-safe in Snowflake?
Fail-safe is a 7-day retention mechanism for disaster recovery beyond the time travel period.
Q5: What is secure data sharing?
It enables sharing data securely across accounts without physically moving it.