diff --git a/renderer/app.js b/renderer/app.js
index 028d7d2..1db0935 100644
--- a/renderer/app.js
+++ b/renderer/app.js
@@ -900,11 +900,17 @@ function scheduleRecentRender() {
 
 // Toggle the .selected class on existing rows without rebuilding the table.
 // Used on click/selection changes — O(rendered rows) instead of O(total rows × sort).
+// Uses getElementsByClassName for the live HTMLCollection (DOM-cached after the
+// first call, auto-tracks insertions/removals on tbody) instead of running a
+// fresh querySelectorAll on every click. At 200 visible rows that's the
+// difference between paying for a tree walk per click vs reading a memoized
+// list that the engine already maintains.
 function applyQueueSelectionClasses() {
   const tbody = document.getElementById('queueBody');
   if (!tbody) return;
-  const rows = tbody.querySelectorAll('.queue-row');
-  for (const tr of rows) {
+  const rows = tbody.getElementsByClassName('queue-row');
+  for (let i = 0; i < rows.length; i++) {
+    const tr = rows[i];
     tr.classList.toggle('selected', selectedJobIds.has(tr.dataset.jobId));
   }
 }
@@ -912,8 +918,9 @@ function applyQueueSelectionClasses() {
 function applyRecentSelectionClasses() {
   const tbody = document.getElementById('recentFilesBody');
   if (!tbody) return;
-  const rows = tbody.querySelectorAll('.recent-file-row');
-  for (const tr of rows) {
+  const rows = tbody.getElementsByClassName('recent-file-row');
+  for (let i = 0; i < rows.length; i++) {
+    const tr = rows[i];
     const order = parseInt(tr.dataset.order, 10);
     tr.classList.toggle('selected', selectedRecentIds.has(order));
   }
diff --git a/tasks/todo.md b/tasks/todo.md
index 0a2e728..8282bdb 100644
--- a/tasks/todo.md
+++ b/tasks/todo.md
@@ -5,12 +5,10 @@
 - ✅ 3.3.1 — `removeFromQueueOnDone` coalesced via microtask (kein O(N²) mehr bei done-Bursts)
 - ✅ 3.3.2 — `fileuploader.log` Auto-Rotation bei 50 MB (max 3 Backups: .1 .2 .3)
 - ✅ 3.3.3 — `_jobLogCollector` Cap auf 1000 tracked jobs (FIFO-eviction beim Überschreiten)
+- ✅ 3.3.4 — `applyQueueSelectionClasses` + `applyRecentSelectionClasses` nutzen `getElementsByClassName` (live HTMLCollection statt querySelectorAll re-query bei jedem Klick)
 
 ## Open items (priorisiert)
 
-### Performance
-- [ ] **`applyQueueSelectionClasses`** (renderer/app.js:891) — `tbody.querySelectorAll` bei jedem Klick. Bei 5000-Jobs-Queue O(N) per click. Cache last rendered range.
-
 ### Code-Qualität
 - [ ] **Test-Coverage für 3.3.0** — keine Tests für die queue-cap-prune-Logik in handleBatchDone, sortQueueJobs dynamic-throttle, log-error-recovery.