Correct Pattern for a Web App (Python Django), server side script with long duration and Database

I have a Web - App (Phyton Django), which allows the User to enter his name in a form. Then the App is doing some serverside calculation (up to 5 min) and saving the result to the database . After that the user is forwarded to another dynamically created side with the results, which are fetched from the database.

My Problem is that when 2 User are searching for the same name, then there are 2 identical threads running. How can I prevent this from happening ?