Delay Job on File upload handler

Hi,

I have developed application with rails 3.0.7 on heroku that target
multiple
user with high volume of uploading file (size aprox 400kb).
My question is, does when one user submit a file, are the instance that
handle the request got bounded to that request so other request will
have
to wait for it to complete ?
Also, does handling this kind of request are better in a delayed job to
improve performance and scalability ?

I really appreciate your help

thanks

Ahmy Y.