Tracking index usage with Insights

This post introduces index usage tracking to PlanetScale Insights. It details how index usage information is extracted from MySQL's InnoDB storage handler via VTGate and aggregated into time-series data. The feature allows users to view index usage per query pattern, search for queries by index usage, and identify unindexed queries. It also explains the limitations of `EXPLAIN` and MySQL's built-in performance schema for this purpose.