diff --git a/.jules/bolt.md b/.jules/bolt.md
index 9345ee7a..688efdb4 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -2,3 +2,8 @@
 
 **Learning:** In Next.js/React applications, when grouping items (like schedules or talks) into a `Map` where the values are arrays, using the array spread operator `[...existing, item]` inside a loop (like `forEach` or `map`) causes amortized O(N^2) memory allocations and unnecessary Garbage Collection overhead.
 **Action:** Always use `.push()` on the existing array reference if the data structure permits local mutation. For strict ESLint configurations enforcing `no-restricted-syntax`, extract the existing array, push to it, and handle the fallback elegantly (`if (!existing) { map.set(key, [item]); } else { existing.push(item); }`).
+
+## 2024-05-23 — O(1) Lookups inside filter loops
+
+**Learning:** `Array.prototype.includes` within `Array.prototype.filter` or `.map` can create O(N*M) bottlenecks if the lookup array is sizable, negatively affecting JS execution time (especially on critical render paths for large lists like schedules).
+**Action:** Always convert lookup arrays to `Set`s before array iteration and use `.has()` for O(1) checks. Ensure to place the `Set` initialization *outside\* any loops. Also, be sure to clean up `.orig` files created by patch tools before committing.
diff --git a/components/schedule/ScheduleContainer.tsx b/components/schedule/ScheduleContainer.tsx
index 33d877a4..4de1fa92 100644
--- a/components/schedule/ScheduleContainer.tsx
+++ b/components/schedule/ScheduleContainer.tsx
@@ -20,7 +20,8 @@ export default function ScheduleContainer({ initialSchedule, year }: Readonly<Sc
       return initialSchedule;
     }
 
-    const filterSessions = (sessions: GridSession[]) => sessions.filter((s) => savedSessionIds.includes(s.id) || s.isServiceSession);
+    const savedSessionIdsSet = new Set(savedSessionIds);
+    const filterSessions = (sessions: GridSession[]) => sessions.filter((s) => savedSessionIdsSet.has(s.id) || s.isServiceSession);
 
     return initialSchedule.map((day) => ({
       ...day,