All-in-one schema:
Post schema (in MongoDB):
id: hash
created: date
updated: date ?
title: string
url: string
picture: blob
content: string
????
comments: array
Comment schema (only inside post schema, not separate entity)
id: hash
UserId: hash
created: date
updated: date
content: string
comments: array
User schema (referenced from comment)
id: hash
created: date
updated: date