diff --git a/.changeset/metal-impalas-brake.md b/.changeset/metal-impalas-brake.md
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+---
+"remix": patch
+"@remix-run/dev": patch
+---
+
+Optimize `parentRouteId` lookup in `defineConventionalRoutes`
+
+Local runs of production Remix builds:
+- Realistic project w/ 700 routes: 10-15s -> <1s (>10x faster)
+- Example project w/ 1,111 routes: 27s -> 0.104s (259x faster)