PERF.46 Website: staff pages with uncached GROUP BY scans: /admin/library/metrics 887 ms, /admin/library 422 ms, /admin/hardware 265 ms

LibraryMetrics::report (LibraryMetrics.php:129, :151, :156) is 430 ms of the metrics page, one statement 222 ms (a 41k-row range on uq_once_a_day, a sort and COUNT(DISTINCT who)), linear in rows (2,157 new rows a day, 4 s at 10x). LibraryVersions::possibleDuplicates (LibraryVersions.php:587-604) is 383 ms per /admin/library view, a self-join over 27k versions that finds nothing today. HardwareReports::summary (HardwareReports.php:93) runs 13 GROUP BY scans of all 25,914 rows (240 ms; idx_day cannot help because every row is inside 90 days). MailLog::countsByStatus (MailLog.php:180) runs twice on /admin/mail (53 ms); RoadmapItems::groups runs seven times on /roadmap-issues with the same arguments. Fix: Cache::remember(…, 600) around report, summary and possibleDuplicates (the dashboard already works this way); better for duplicates, set duplicate_of_version_id at publish time in LibraryVersions::create (one indexed lookup on idx_item_sha / idx_source_sha) and list that; for metrics a nightly library_metrics_daily rollup or at least a covering index (day, kind, ref, action, who) and drop the redundant idx_day; call countsByStatus and groups once per request and pass the value down.