# A daily revenue dashboard reads from a lake fact partitioned by user_id, producing 10 million tiny p

Canonical URL: <https://datadriven.io/problems/a-daily-revenue-dashboard-reads-from-a-lake-fact-partitioned-b56c89dc>

Domain: Pipeline Design · Difficulty: medium

## Problem

A daily revenue dashboard reads from a lake fact partitioned by user_id, producing 10 million tiny per-user directories. Daily-filter queries cannot prune because the partition key does not match the filter. Apply the section's partitioning framing and replace the wrong partition key with a section-named canonical date key. The high-cardinality key belongs on a clustering key, not a partition key.

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