Comprehensive and Detailed Explanation From Exact Extract:
Exact extract: "A shallow clone creates a copy of the metadata that references the source data files; it is fast and inexpensive." Exact extract: "A deep clone copies the data." Exact extract: "Clones provide a point-in-time snapshot for experimentation without impacting the source." A shallow clone of the production Delta table creates an instantaneous snapshot that references the same data files, so it introduces virtually no downtime or storage overhead and avoids interfering with the ongoing ETL. A deep clone would copy all data (very expensive and slow for 20B rows). CTAS rewrites data and is unnecessary; direct access to prod risks contention and accidental changes.