But that said, yes, a forum is a good use case for a relational database, though we wanted to try something new with a NoSQL solution. Redis worked well and still does, though there are areas or improvement to be made in MongoDB, and most involve dropping Redis support at some point down the line.
Dropping redis will make me sad since I setup my forum with the redis recommendation from the documentation :(
You'll have to publicize the secret sauce you use to convert from redis to Mongo.
Yes, if they would release that, it would be great and then they can drop Redis support at will.