diff --git a/cmd/updater/function.py b/cmd/updater/function.py
new file mode 100644
index 0000000..4ac430e
--- /dev/null
+++ b/cmd/updater/function.py
@@ -0,0 +1,110 @@
+import youtube_dl
+
+BEST_FORMAT = "bestvideo+bestaudio/best"
+
+FORMATS = {
+    'video_high': 'best[ext=mp4]',
+    'video_low': 'worst[ext=mp4]',
+    'audio_high': 'bestaudio',
+    'audio_low': 'worstaudio',
+}
+
+
+def handler(event, context):
+    url = event['url']
+    if not url:
+        raise ValueError('Invalid resource URL %s' % url)
+
+    start = int(event['start'])
+    if not start or start is None or start < 1:
+        start = 1
+
+    end = int(event['end'])
+    if end > 600:
+        end = 600
+
+    if start > end:
+        raise ValueError('Invalid start/end range')
+
+    kind = event['kind']
+    if not kind:
+        kind = 'video_high'
+
+    last_id = event['last_id']
+
+    print('Getting updated for %s (start=%d, end=%d, kind: %s, last id: %s)', url, start, end, kind, last_id)
+    return _get_updates(start, end, url, kind, last_id)
+
+
+def _get_updates(start, end, url, kind, last_id=None):
+    opts = {
+        'playliststart': start,
+        'playlistend': end,
+        'extract_flat': 'in_playlist',
+        'quiet': True,
+        'no_warnings': True,
+        'simulate': True,
+        'skip_download': True,
+    }
+
+    with youtube_dl.YoutubeDL(opts) as ytdl:
+        selector = ytdl.build_format_selector(FORMATS[kind])
+        feed_info = ytdl.extract_info(url, download=False)
+
+        # Record basic feed metadata
+        feed = {
+            'id': feed_info.get('id'),
+            'title': feed_info.get('uploader'),
+            'page_url': feed_info.get('webpage_url'),
+        }
+
+        videos = []
+        new_last_id = None
+
+        entries = feed_info['entries']
+        for idx, entry in enumerate(entries):
+            # Query video metadata from YouTube
+            result = ytdl.process_ie_result(entry, download=False)
+
+            video_id = result['id']
+
+            # If already seen this video previously, stop pulling updates
+            if last_id and video_id == last_id:
+                break
+
+            # Remember new last id
+            if idx == 0:
+                new_last_id = video_id
+
+            videos.append({
+                'id': video_id,
+                'title': result.get('title'),
+                'description': result.get('description'),
+                'thumbnail': result.get('thumbnail'),
+                'duration': result.get('duration'),
+                'video_url': result.get('webpage_url'),
+                'upload_date': result.get('upload_date'),
+                'ext': result.get('ext'),
+                'size': _get_size(result, selector),
+            })
+
+    return {
+        'feed': feed,
+        'items': videos,
+        'last_id': new_last_id,
+    }
+
+
+def _get_size(video, selector):
+    try:
+        selected = next(selector(video))
+    except KeyError:
+        selected = video
+
+    if 'requested_formats' in selected:
+        return sum(int(f['filesize']) for f in selected['requested_formats'])
+
+    if selected.get('filesize') is not None:
+        return int(selected['filesize'])
+
+    return 0
diff --git a/cmd/updater/function_test.py b/cmd/updater/function_test.py
new file mode 100644
index 0000000..d949934
--- /dev/null
+++ b/cmd/updater/function_test.py
@@ -0,0 +1,22 @@
+import function
+import unittest
+
+
+class TestUpdater(unittest.TestCase):
+    def test_get_updates(self):
+        kinds = ['video_high', 'video_low', 'audio_high', 'audio_low']
+        for kind in kinds:
+            with self.subTest(kind):
+                result = function._get_updates(1, 2, 'https://www.youtube.com/user/CNN/videos', kind)
+                self.assertIsNotNone(result['feed'])
+                self.assertIsNotNone(result['items'])
+
+    def test_get_change_list(self):
+        result = function._get_updates(1, 5, 'https://www.youtube.com/user/CNN/videos', 'video_low')
+        self.assertEqual(len(result['items']), 5)
+        self.assertEqual(result['items'][0]['id'], result['last_id'])
+        last_id = result['items'][2]['id']
+        self.assertIsNotNone(last_id)
+        result = function._get_updates(1, 5, 'https://www.youtube.com/user/CNN/videos', 'video_low', last_id)
+        self.assertEqual(len(result['items']), 2)
+        self.assertEqual(result['items'][0]['id'], result['last_id'])
diff --git a/cmd/updater/requirements.txt b/cmd/updater/requirements.txt
new file mode 100644
index 0000000..930b5e4
--- /dev/null
+++ b/cmd/updater/requirements.txt
@@ -0,0 +1 @@
+youtube_dl==2019.03.09