Hello @Richard-Cesar, thanks for the comments!
Currently, for this forum, at 193 Topics and 905 Posts, our redis instance is using 6.78M, as reported by redis, with a memory fragmentation ratio of 1.19.
A clean install uses 433.88K.
The part of NodeBB that takes up the most space would be the actual post content, and to address this, we're building a set of "otherDB" plugins so that post content (at minimum) can be persisted to a disk-based data store, at which point the redis key containing the post data would have an
EXPIRE set, allowing redis to function more like a supercache for posts.
The same concept can be extended for topics and such, if the need arises.
User avatar uploads are stored to disk, while drag-and-drop image uploading is uploaded to imgur (if set up with an imgur key, otherwise the functionality is disabled).
For web socket fallbacks, we use the fallbacks as designed in socket.IO -- websockets fall back to xhr polling, then jsonp polling. I do not believe we enabled flashsockets, although I could be wrong.