diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..1f04648
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-05-23 - Pre-indexing Derived Properties for Faster Filtering
+**Learning:** In vanilla JS applications with large lists, filtering performance can degrade significantly when searching involves concatenating strings or checking dates inline inside the filter callback (`pdfDatabase.filter()`). For example, doing `.toLowerCase().includes()` on multiple fields per item.
+**Action:** Pre-calculate a `_searchStr` (and other derived properties like `_isNew` and `_formattedDate`) during the initial data load (`loadPDFDatabase`) exactly once. Use this pre-calculated string inside the filter/render loop for O(1) property access and faster substring searching. Add early returns to skip further checks if a condition fails.
diff --git a/script.js b/script.js
index ef463ba..55c1691 100644
--- a/script.js
+++ b/script.js
@@ -452,6 +452,23 @@ async function syncClassSwitcher() {
     renderSemesterTabs();
 }
 
+function prepareSearchIndex(pdfs) {
+    const dateFormatter = new Intl.DateTimeFormat('en-US', {
+        year: 'numeric', month: 'short', day: 'numeric'
+    });
+    const now = new Date();
+    const sevenDaysMs = 7 * 24 * 60 * 60 * 1000;
+
+    pdfs.forEach(pdf => {
+        pdf._searchStr = `${pdf.title} ${pdf.description || ''} ${pdf.category || ''} ${pdf.author || ''}`.toLowerCase();
+
+        const uploadDateObj = new Date(pdf.uploadDate);
+        const timeDiff = now - uploadDateObj;
+        pdf._isNew = !isNaN(uploadDateObj) ? (timeDiff < sevenDaysMs) : false;
+        pdf._formattedDate = !isNaN(uploadDateObj) ? dateFormatter.format(uploadDateObj) : 'Unknown Date';
+    });
+}
+
 async function loadPDFDatabase() {
     if (isMaintenanceActive) return;
 
@@ -490,6 +507,7 @@ async function loadPDFDatabase() {
 
         if (shouldUseCache) {
             pdfDatabase = cachedData;
+            prepareSearchIndex(pdfDatabase);
             // --- FIX: CALL THIS TO POPULATE UI ---
             syncClassSwitcher();
             renderSemesterTabs();
@@ -513,6 +531,7 @@ async function loadPDFDatabase() {
             data: pdfDatabase
         }));
 
+        prepareSearchIndex(pdfDatabase);
         // --- FIX: CALL THIS TO POPULATE UI ---
         syncClassSwitcher();
         renderPDFs();
@@ -948,26 +967,21 @@ function renderPDFs() {
 
     // Locate renderPDFs() in script.js and update the filter section
     const filteredPdfs = pdfDatabase.filter(pdf => {
-        const matchesSemester = pdf.semester === currentSemester;
+        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;
+        if (pdf.class !== currentClass) return false;
 
-        let matchesCategory = false;
         if (currentCategory === 'favorites') {
-            matchesCategory = favorites.includes(pdf.id);
+            if (!favorites.includes(pdf.id)) return false;
         } else {
-            matchesCategory = currentCategory === 'all' || pdf.category === currentCategory;
+            if (currentCategory !== 'all' && 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);
+        if (searchTerm && pdf._searchStr && !pdf._searchStr.includes(searchTerm)) return false;
 
-        // Update return statement to include matchesClass
-        return matchesSemester && matchesClass && matchesCategory && matchesSearch;
+        return true;
     });
 
     updatePDFCount(filteredPdfs.length);
@@ -1037,9 +1051,12 @@ 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
+    let isNew = pdf._isNew;
+    if (isNew === undefined) {
+        const uploadDateObj = new Date(pdf.uploadDate);
+        const timeDiff = new Date() - uploadDateObj;
+        isNew = timeDiff < (7 * 24 * 60 * 60 * 1000); // 7 days
+    }
 
     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>`
@@ -1054,9 +1071,12 @@ 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'
-    });
+    let formattedDate = pdf._formattedDate;
+    if (formattedDate === undefined) {
+        formattedDate = new Date(pdf.uploadDate).toLocaleDateString('en-US', {
+            year: 'numeric', month: 'short', day: 'numeric'
+        });
+    }
 
     // Uses global escapeHtml() now