fractal trees should have a faster read performance with leveldb with a comparable updating performance. There does not exist any open source solution for such structure, while we could hope that www.acunu.com might provide an open source solution for similary Stratified B-tree http://www.acunu.com/2011/04/log-file-systems-and-ssds-made-...

Being in-kernel, acunu is very far from the lightness of LevelDB.

Is there a more useful technical paper on Fractal Trees? Better yet is there a open source implementation of the same?

Cache-oblivious streaming B-trees:

http://supertech.csail.mit.edu/papers/sbtree.pdf

I don't know for certain any open-source implementation, but I have heard COLAs are used in HBase.