Diagnostic canary. The Liveness KPI runs a real query against the database — if it shows a number, the QuickSight rendering pipeline is healthy and any blank visual on another sheet indicates a data or SQL issue. If the KPI is blank, QuickSight itself is broken.
Count of public-schema tables. Real query against the database via Direct Query -- if this shows a number, QuickSight's rendering pipeline is healthy. Blank means QuickSight itself is broken (not the data, not the SQL).
Row counts + most-recent date per matview (and base tables for comparison). Freshly-loaded matviews showing 0 mean the ETL has not refreshed them yet. If a base table's `latest_date` moves past a matview's `latest_date`, the matview is stale relative to fresh ETL data — re-run `recon-gen data refresh --execute`.