I have seen quite a few code samples/plugins that promote uploading assets directly to S3. For example, if you have a user object with an avatar, the file upload field would load directly to S3.
The only way I see this being possible is if the user object is already created in the database and your S3 bucket + path is something like
user_avatars.domain.com/some/id/partition/medium.jpg
But then if you had an image tag that tried to access that URL when an avatar was not uploaded, it would yield a bad result. How would you handle checking for existence?
Also, it seems like this would not work well for most has many associations. For example, if a user had many songs/mp3s, where would you store those and how would you access them.
Also, your validations will be shot.
I am having trouble thinking of situations where direct upload to S3 (or any cloud) is a good idea and was hoping people could clarify either proper use cases, or tell me why my logic is incorrect.