What is the design pattern for file upload

I got the below question from one of the interview.
In Web application:
Step 1: Upload the file (pdf, txt, excel, doc) through Multi-part component.
Step 2: Server side code receiving the file and validate the uploaded file.
Step 3: After validate the file, it has pass to different system
Please share me your idea, Which design pattern is opt for the above process.

Thanks in advance.