diff --git a/backend/__tests__/services/videoPlaceholderNoDbLookup.test.js b/backend/__tests__/services/videoPlaceholderNoDbLookup.test.js
new file mode 100644
index 00000000..78efac31
--- /dev/null
+++ b/backend/__tests__/services/videoPlaceholderNoDbLookup.test.js
@@ -0,0 +1,62 @@
+/**
+ * generateVideoPlaceholder() must not touch the database when the caller
+ * already supplies width/height (videoProcessor.js's thumbnail-generation
+ * fallback does exactly this).
+ *
+ * Why it matters: processUploadedPhotos() (chunked video upload) holds a
+ * per-file SQLite transaction open across thumbnail generation. SQLite's
+ * knex pool defaults to a single connection, so any second, un-transacted
+ * db() query made while that transaction is open blocks until
+ * acquireConnectionTimeout (60s in production) — verified directly against
+ * an isolated SQLite db (codex review of #1371/#1372). Passing explicit
+ * dimensions must skip getThumbnailSettings()'s db() call entirely, not
+ * just tolerate its failure.
+ */
+
+const path = require('path');
+const fs = require('fs').promises;
+const os = require('os');
+
+const mockDbSpy = jest.fn(() => {
+  throw new Error('db() must not be called when width/height are supplied');
+});
+jest.mock('../../src/database/db', () => ({ db: (...args) => mockDbSpy(...args) }));
+
+const storageModule = require('../../src/services/storage');
+const LocalFsStorage = require('../../src/services/storage/LocalFsStorage');
+
+describe('generateVideoPlaceholder skips the settings DB lookup given explicit dimensions', () => {
+  let storage;
+  let root;
+  let imageProcessor;
+
+  beforeAll(async () => {
+    root = await fs.mkdtemp(path.join(os.tmpdir(), 'picpeak-vidplaceholder-'));
+    storage = new LocalFsStorage({ root });
+    await storage.init();
+    storageModule.setStorageForTesting(storage);
+    imageProcessor = require('../../src/services/imageProcessor');
+  }, 30000);
+
+  afterAll(async () => {
+    storageModule.resetStorage();
+    await fs.rm(root, { recursive: true, force: true }).catch(() => {});
+  });
+
+  afterEach(() => mockDbSpy.mockClear());
+
+  it('never calls db() when width/height are provided', async () => {
+    const key = await imageProcessor.generateVideoPlaceholder('demo.mp4', { width: 300, height: 300 });
+
+    expect(key).toBe('thumbnails/thumb_demo.jpg');
+    expect(await storage.exists(key)).toBe(true);
+    expect(mockDbSpy).not.toHaveBeenCalled();
+  });
+
+  it('falls through to defaults (not a throw) when db() fails and no dimensions were given', async () => {
+    const key = await imageProcessor.generateVideoPlaceholder('demo2.mp4');
+
+    expect(key).toBe('thumbnails/thumb_demo2.jpg');
+    expect(mockDbSpy).toHaveBeenCalled();
+  });
+});
diff --git a/backend/src/services/__tests__/videoProcessor.test.js b/backend/src/services/__tests__/videoProcessor.test.js
index cf650a2b..ec88190c 100644
--- a/backend/src/services/__tests__/videoProcessor.test.js
+++ b/backend/src/services/__tests__/videoProcessor.test.js
@@ -4,7 +4,9 @@ jest.mock('../storage', () => ({
   getStorage: jest.fn()
 }));
 jest.mock('../imageProcessor', () => ({
-  generateVideoPlaceholder: jest.fn()
+  generateVideoPlaceholder: jest.fn(),
+  DEFAULT_THUMBNAIL_WIDTH: 300,
+  DEFAULT_THUMBNAIL_HEIGHT: 300
 }));
 
 const ffmpeg = require('fluent-ffmpeg');
@@ -98,7 +100,10 @@ describe('processUploadedVideo degrades gracefully instead of rejecting the whol
     expect(result.metadata).toEqual(expect.objectContaining({ duration: 5, videoCodec: 'h264' }));
     // thumbnailKey is always thumbnails/thumb_<name>.jpg — strip the prefix
     // back to a filename so generateVideoPlaceholder recomputes the same key.
-    expect(generateVideoPlaceholder).toHaveBeenCalledWith('wedding_001.jpg');
+    // Explicit width/height so generateVideoPlaceholder skips its DB-backed
+    // settings lookup — this can run inside an open per-file SQLite
+    // transaction (chunked video upload), where that lookup deadlocks.
+    expect(generateVideoPlaceholder).toHaveBeenCalledWith('wedding_001.jpg', { width: 300, height: 300 });
     expect(result.thumbnailKey).toBe('thumbnails/thumb_placeholder.jpg');
     expect(storage.putFromFile).not.toHaveBeenCalled();
   });
diff --git a/backend/src/services/imageProcessor.js b/backend/src/services/imageProcessor.js
index 9ba0b554..9485b403 100644
--- a/backend/src/services/imageProcessor.js
+++ b/backend/src/services/imageProcessor.js
@@ -369,9 +369,15 @@ async function generateVideoPlaceholder(originalFilename, options = {}) {
   const thumbnailRelKey = path.posix.join('thumbnails', thumbnailFilename);
   const storage = getStorage();
 
-  const settings = await getThumbnailSettings();
-  const width = settings.width || DEFAULT_THUMBNAIL_WIDTH;
-  const height = settings.height || DEFAULT_THUMBNAIL_HEIGHT;
+  // Skip the settings lookup when the caller already supplies dimensions.
+  // This can run from inside an open per-file SQLite transaction (chunked
+  // video upload's fallback path in videoProcessor.js) — a second,
+  // un-transacted db() query for settings there deadlocks against SQLite's
+  // single-connection pool until acquireConnectionTimeout (60s), reproduced
+  // directly against an isolated SQLite db (codex review of #1371/#1372).
+  const settings = (options.width && options.height) ? {} : await getThumbnailSettings();
+  const width = options.width || settings.width || DEFAULT_THUMBNAIL_WIDTH;
+  const height = options.height || settings.height || DEFAULT_THUMBNAIL_HEIGHT;
 
   if (options.regenerate) {
     await storage.delete(thumbnailRelKey).catch(() => {});
@@ -864,4 +870,6 @@ module.exports = {
   ensurePreviewImage,
   extractCaptureDate,
   withLocalCopy,
+  DEFAULT_THUMBNAIL_WIDTH,
+  DEFAULT_THUMBNAIL_HEIGHT,
 };
diff --git a/backend/src/services/videoProcessor.js b/backend/src/services/videoProcessor.js
index 803e351f..21182532 100644
--- a/backend/src/services/videoProcessor.js
+++ b/backend/src/services/videoProcessor.js
@@ -190,9 +190,20 @@ async function processUploadedVideo(videoPath, thumbnailKey, options = {}) {
   // a filename so generateVideoPlaceholder recomputes this exact same key.
   if (!generatedThumbnailKey) {
     try {
-      const { generateVideoPlaceholder } = require('./imageProcessor');
+      const {
+        generateVideoPlaceholder,
+        DEFAULT_THUMBNAIL_WIDTH,
+        DEFAULT_THUMBNAIL_HEIGHT
+      } = require('./imageProcessor');
       const placeholderFilename = path.basename(thumbnailKey).replace(/^thumb_/, '');
-      const placeholderKey = await generateVideoPlaceholder(placeholderFilename);
+      // Explicit width/height make generateVideoPlaceholder skip its
+      // configured-thumbnail-size DB lookup (see its own comment) — this
+      // call can run from inside processUploadedPhotos' open per-file
+      // SQLite transaction, where that lookup would otherwise deadlock.
+      const placeholderKey = await generateVideoPlaceholder(placeholderFilename, {
+        width: DEFAULT_THUMBNAIL_WIDTH,
+        height: DEFAULT_THUMBNAIL_HEIGHT
+      });
       if (placeholderKey) {
         generatedThumbnailKey = placeholderKey;
       }