C# mongodb model like Facebook

Question

I'm working on a project where the MongoDB model will be similar to Facebook. So we all know how FB works, a user "likes" a band/company page, and that user will see all the posts from that page.

Is the below model how I should design this? If a Page has million likes, then each Post will have a million sub documents of Like. That does not seem right, there must be a better way that I cant think of.

Thanks.

public class Person
{
    public ObjectId Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class Page
{
    public ObjectId Id { get; set; }
    public string Name { get; set; }
    public List<Like> PersonLikes { get; set; }

}
public class Like
{
    public ObjectId Id { get; set; }
    public ObjectId UserId { get; set; }
    public DateTime DateLiked { get; set; }
}

public class Post
{
    public ObjectId Id { get; set; }
    public ObjectId PageId { get; set; }
    public string Message { get; set; }
    public List<Like> PersonLikes { get; set; }
}

Answer 1

My take assuming you only want to track likes

public class Page
{
    public ObjectId Id { get; set; }
    public DateTimeOffset Date { get; set; }
    public string Name { get; set; }
    public int NumberOfLikes { get; set; }
}

public class Post
{
    public ObjectId Id { get; set; }
    public ObjectId PageId { get; set; }
    public DateTimeOffset Date { get; set; }
    public string Message { get; set; }
    public int NumberOfLikes { get; set; }
}

I would then queue the Reaction (Like or Dislike) for insertion, "sentiment" information doesn't have to be stored in real time, does it? These are not medications, bank transactions, etc.

public class Like
{
    public ObjectId Id { get; set; }
    public ObjectId ParentId { get; set;}
    public ObjectId UserId { get; set; }
    public DateTimeOffset Date { get; set; }
}

Queue where? to a collection of Likes. Why not part of the page or post? Because if a post goes viral (as you said even though the majority won't), you may end up with a 1,000,000 likes. Who is going to browse this information other than an analytic engine?

You also have to ensure a user can only express their reaction only once per item.

Answer 2

The post only exists on one page so it´s the page that should own the post, not the post owning the page.

public class Person
{
    public ObjectId Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class Page
{
    public ObjectId Id { get; set; }
    public string Name { get; set; }
    public List<Like> PersonLikes { get; set; }
    public List<Post> Posts { get; set; }
}

public class Post
{
    public ObjectId Id { get; set; }
    public string Message { get; set; }
    public List<Like> Likes { get; set; }
}

public class Like
{
    public ObjectId Id { get; set; }
    public ObjectId UserId { get; set; }
    public DateTime DateLiked { get; set; }
}