diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..8b3d054
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2025-02-17 - [Pre-Calculate Expensive Fields for Search/Filter]
+**Learning:** Performing multiple Date instantiation, toLowerCase conversions, and string formatting inside high-frequency UI render loops like `renderPDFs` creates significant CPU overhead, especially as the size of `pdfDatabase` grows.
+**Action:** Always map the dataset once during the initial data load (`loadPDFDatabase`) to pre-calculate and cache expensive derived strings/flags on the objects (e.g. `_searchStr`, `_formattedDate`, `_isNew`), then use simple accessors and fast equality checks in the filter array callbacks. Add these properties AFTER the raw JSON payload is cached to localStorage to prevent cache bloat.
diff --git a/script.js b/script.js
index 22f399d..9ffb987 100644
--- a/script.js
+++ b/script.js
@@ -338,6 +338,39 @@ function getAdData(slotName) {
 /* =========================================
    5. DATA LOADING WITH CACHING
    ========================================= */
+
+/**
+ * ⚡ Bolt Optimization: Pre-calculate expensive runtime properties
+ * What: Calculates `_searchStr`, `_formattedDate`, and `_isNew` once during data load.
+ * Why: Prevents creating Date objects and concatenating/lowercasing strings on every keystroke in `renderPDFs()`.
+ * Impact: Significantly reduces CPU overhead during list rendering and filtering, speeding up search.
+ */
+function prepareSearchIndex(database) {
+    const now = new Date();
+    database.forEach(pdf => {
+        // Handle Date (Firestore Timestamp vs ISO string from cache)
+        let uploadDateObj;
+        if (pdf.uploadDate && typeof pdf.uploadDate.toDate === 'function') {
+            uploadDateObj = pdf.uploadDate.toDate();
+        } else {
+            uploadDateObj = new Date(pdf.uploadDate);
+        }
+
+        pdf._formattedDate = uploadDateObj.toLocaleDateString('en-US', {
+            year: 'numeric', month: 'short', day: 'numeric'
+        });
+
+        const timeDiff = now - uploadDateObj;
+        pdf._isNew = timeDiff < (7 * 24 * 60 * 60 * 1000); // 7 days
+
+        const title = pdf.title || '';
+        const desc = pdf.description || '';
+        const cat = pdf.category || '';
+        const author = pdf.author || '';
+        pdf._searchStr = `${title} ${desc} ${cat} ${author}`.toLowerCase();
+    });
+}
+
 function renderSemesterTabs() {
     const container = document.getElementById('semesterTabsContainer');
     if (!container) return;
@@ -454,6 +487,7 @@ async function loadPDFDatabase() {
 
         if (shouldUseCache) {
             pdfDatabase = cachedData;
+            prepareSearchIndex(pdfDatabase); // ⚡ Bolt: Pre-calculate index
             // --- FIX: CALL THIS TO POPULATE UI ---
             syncClassSwitcher();
             renderSemesterTabs();
@@ -477,6 +511,7 @@ async function loadPDFDatabase() {
             data: pdfDatabase
         }));
 
+        prepareSearchIndex(pdfDatabase); // ⚡ Bolt: Pre-calculate index AFTER caching raw data
         // --- FIX: CALL THIS TO POPULATE UI ---
         syncClassSwitcher();
         renderPDFs();
@@ -905,26 +940,22 @@ function renderPDFs() {
 
     // Locate renderPDFs() in script.js and update the filter section
     const filteredPdfs = pdfDatabase.filter(pdf => {
-        const matchesSemester = pdf.semester === currentSemester;
+        // ⚡ Bolt Optimization: Early Returns for cheaper checks
+        if (pdf.class !== currentClass) return false;
+        if (pdf.semester !== currentSemester) return false;
 
-        // NEW: Check if the PDF class matches the UI's current class selection
-        // Note: If old documents don't have this field, they will be hidden.
-        const matchesClass = pdf.class === currentClass;
-
-        let matchesCategory = false;
         if (currentCategory === 'favorites') {
-            matchesCategory = favorites.includes(pdf.id);
-        } else {
-            matchesCategory = currentCategory === 'all' || pdf.category === currentCategory;
+            if (!favorites.includes(pdf.id)) return false;
+        } else if (currentCategory !== 'all') {
+            if (pdf.category !== currentCategory) return false;
         }
 
-        const matchesSearch = pdf.title.toLowerCase().includes(searchTerm) ||
-            pdf.description.toLowerCase().includes(searchTerm) ||
-            pdf.category.toLowerCase().includes(searchTerm) ||
-            pdf.author.toLowerCase().includes(searchTerm);
+        // ⚡ Bolt Optimization: Use pre-calculated search string
+        if (searchTerm && pdf._searchStr) {
+            if (!pdf._searchStr.includes(searchTerm)) return false;
+        }
 
-        // Update return statement to include matchesClass
-        return matchesSemester && matchesClass && matchesCategory && matchesSearch;
+        return true;
     });
 
     updatePDFCount(filteredPdfs.length);
@@ -994,9 +1025,9 @@ function createPDFCard(pdf, favoritesList, index = 0, highlightRegex = null) {
     const heartIconClass = isFav ? 'fas' : 'far';
     const btnActiveClass = isFav ? 'active' : '';
 
-    const uploadDateObj = new Date(pdf.uploadDate);
-    const timeDiff = new Date() - uploadDateObj;
-    const isNew = timeDiff < (7 * 24 * 60 * 60 * 1000); // 7 days
+    // ⚡ Bolt Optimization: Use pre-calculated flags/strings instead of Date math in loops
+    const isNew = pdf._isNew || false;
+    const formattedDate = pdf._formattedDate || '';
 
     const newBadgeHTML = isNew
         ? `<span style="background:var(--error-color); color:white; font-size:0.6rem; padding:2px 6px; border-radius:4px; margin-left:8px; vertical-align:middle;">NEW</span>`
@@ -1010,11 +1041,6 @@ function createPDFCard(pdf, favoritesList, index = 0, highlightRegex = null) {
     };
     const categoryIcon = categoryIcons[pdf.category] || 'fa-file-pdf';
 
-    // Formatting Date
-    const formattedDate = new Date(pdf.uploadDate).toLocaleDateString('en-US', {
-        year: 'numeric', month: 'short', day: 'numeric'
-    });
-
     // Uses global escapeHtml() now
 
     const highlightText = (text) => {