Patterns for building social network type applications?

Question

I need to design / architect / develop a web based social network type application.

Basic functionality:
- users create accounts on the system
- users agree to

Answer 1

As Aaroon pointed out, you should first ask youself what problem you want to solve.

What content do you want people to share? Should it really be visible only to friends? It is much easier and scalable if you make content publicly visible, because what content is displayed is not dependent on who is watching the page and you can cache it easily. Publicly available user-generated content attracts new users.

If you want to restrict access and give to the user the opportunity to attach groups of friends to a resource I would go with a simple group-based access control. Let each resource have a group of users which can edit the resource and a group of users who can see it.

That way each resource has two single value attributes, and each user belons to a finite number of group. You can attach the view-group and edit-group attributes to a document stored in a NOSQL database, a search engine like Lucene/Sphinx or a row in a SQL database. When querying for content available for the user, pass all groups the user belongs to (in SQL you would use IN clause, in Sphinx setFilter('view-group', array(2,3,4)). The database would return only content available for the user. Because you are attaching only 2 integer values (view-group and edit-group) to a document, you can store them in memory which makes the search fast and scalable.