BI-ready aggregate views

Marts are the source of truth. Agg views are pre-aggregated rollups that Looker can read directly. Four agg views in this project: seller performance, product performance, product sales by time, and customer purchase summary.

Aggregate views save BigQuery cost. A Looker dashboard that scans 100M fact rows on every load is expensive. The same query run against a pre-aggregated view that has 5K rows is cheap. dbt rebuilds the view on a schedule.

BigQuery materialized views auto-refresh but have constraints (no joins to non-base tables, no UDFs). dbt views run on dbt schedule, no constraints. The course uses dbt views for max flexibility. Mature stacks combine both.