mongo db or redis for a facebook like site?
There's a huge distinction to be made between Redis and MongoDB for your particular needs, in that Redis, unlike MongoDB, doesn't facilitate value queries.
You can use MongoDB to embed the comments within the post document, which means you get the post and the comments in a single query, yet you could also query for post documents based on tags, the author, etc.
You'll definitely want to go with MongoDB. Redis is great, but it's not a proper fit for what I'd believe you'll need from it.
I'm building a social app in django, the architecture of the site will be very similar to facebook
There will be posts, posts will have comments
Both posts and comments will have meta data like date, author, tags, votes
I decided to go with nosql database because of the ease with which we can add new features.
I finalized on mongodb as i can easily store a post and its comments in a single document. I'm having second thoughts now, would REDIS be better than mongo for this kind of app?
Update:
I have decided to go with mongodb, will use redis for user home page and home page if necessary.