The legacy filter queries projected ItemValue before grouping tags and genres. EF Core translated that shape into duplicated correlated aggregates, causing multi-minute requests for libraries with many distinct values and blocking unrelated SQLite-backed API calls.
Join ItemValuesMap directly to ItemValues before grouping. This preserves type and item filtering, clean-value grouping, minimum-value selection and ordering while producing one aggregate query. Add an in-memory SQLite regression test for result semantics and both SQL shapes.
Felix Förtsch