PayPal Senior Software Engineer interview questions

Here's the problem the questions were not difficult, just so basic and uncomplicated "Design for me a web application". I can do that in a "Hello World" socket connection. Now what do you what it to do? ....or I can design a Web Application that does it all...

On scalability (there is no one right/ wrong answer though) How will you transfer a huge dataset from one platform to other given all technology stack