**Architectural Logic**: Time Travel enables historical query and recovery—retention affects cost. **Mechanism**: Query at point: `AT(OFFSET => -3600)` or `AT(TIMESTAMP => '...')`. Restore: `UNDROP TABLE`. Clone: `CREATE TABLE t_clone CLONE t AT(OFFSET => -86400)`....
This easy-level SQL question appears frequently in data engineering interviews at companies like Cognizant. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (snowflake) will help you answer variations of this question confidently.
Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.
Architectural Logic: Time Travel enables historical query and recovery—retention affects cost. Mechanism: Query at point: AT(OFFSET => -3600) or AT(TIMESTAMP => '...'). Restore: UNDROP TABLE. Clone: CREATE TABLE t_clone CLONE t AT(OFFSET => -86400). Retention: 1 day default; up to 90 days for enterprise. Use: Debugging; recovery; historical analysis. Scalability: Retention period limits. Cost: Storage for historical data; longer retention = more cost. Best Practice: Use for accidental delete recovery; clone before major changes; document retention policy.
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Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.