Why Parquet?

Concepts: paColumnarVsRow, paCompression

The harder version of this question is "When would you NOT use Parquet?" If you only say "it's columnar and compresses well," you've given a surface-level answer. The interviewer wants to hear the exceptions, the tradeoffs, and when other formats win. When Parquet Hurts The stronger signal is knowing when NOT to use Parquet, not reciting its benefits. Your interviewer expects you to lead with the failure modes: high-frequency writes, row-level access patterns, and small payloads are the three scenarios where Parquet works against you. Streaming ingestion produces thousands of small Parquet files per minute. Each file carries ~4 KB of footer metadata. At 1,000 files/minute over 24 hours, you have 1.44 million files where metadata overhead exceeds the data itself. Parquet's row group structu