How can i return custom response json error when object is older then 8 minutes.

Here is my code, but response doesn't work:

```
def perform_update(self, serializer):
    instance = serializer.save()
    diff_minutes = (datetime.now() - instance.ordered_date).total_seconds() / 60
    if diff_minutes > 8:
        return Response({'expired': True}, status=status.HTTP_500_INTERNAL_SERVER_ERROR)
    self.post_save(instance)

```

Same this is when i use `post_save`.

I don't get any response, it always pass.

Any suggestion?