Comprehensive and Detailed 150 to 250 words of Explanation From Snowflake SnowPro Architect exam scope and all publicly documented material:
Clustering keys are most beneficial when they improve micro-partition pruning for common filter patterns and when the chosen columns provide a useful ordering that co-locates data. A common heuristic is to place lower- cardinality columns earlier (to quickly narrow partitions) and then add a higher-cardinality column that further reduces scanned partitions for selective access paths. Here, C_DATE has very low NDV (110), making it an excellent leading key to organize data by date and enable strong pruning for time-bound queries typical of event tables. Next, A_ID (11K) is moderate cardinality and can further segment data within a date range, helping point lookups or narrow scans by identifier. For the third key, the options force choosing between very high-cardinality event activity columns; selecting EVENT_ACT_0 (1.1G) is preferable to EVENT_ACT_4 (2.2G) because it is comparatively less distinct while still supporting additional pruning when queries filter by that attribute. This ordering aligns with Snowflake guidance: keep keys few, ordered to match common predicates, and avoid excessively high-cardinality keys unless they directly match frequent selective filters.
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