What is the architecture of a website like Shopify?

I am reading about software architecture of different websites/web application. I know this question might be a bit general but any hints would be really appreciated.

Let's say we know how a single online shop works, how do we expand it to a platform like Shopify where people can create their own shops and then deploy it on the web?

Do you think developing such a platform is doable with a full-stack framework such as MeteorJS ?

Thank you so much, Amir