```dart
Future<void> updatePost() async {
  final postsWithId = await Amplify.DataStore.query(
    Post.classType,
    where: Post.ID.eq('123'),
  );

  final oldPost = postsWithId.first;
  final newPost = oldPost.copyWith(id: oldPost.id, title: 'Updated Title');

  await Amplify.DataStore.save(newPost);
}
```