This is going to come off as abit negative but I kinda feel it has to be said. I would first like to say I do love the Fractal tree indexing, very cool and could have alot more intesting usecases outside of databases (I'm thinking logical volume/block storage etc.. I'm always thinking in kernel land..)

The problem is that Mongo advertised itself as a database and wasn't one. Once you do that reputation of the product is dead forever.

TokuMX is a real database as far as I can see, MVCC, great indexing story etc.

By association TokuMX is probably not regarded as highly as it should be. Which is a shame but it's a people problem, not a technical one. People can very easily lose trust in a technology at which point it's effectively dead, it might take a long time to die due to lock-in but it's dead.

For instance I have recently started playing with RethinkDB over TokuMX almost purely because of Mongo association.

Now technically that might not sound like good reasoning but when you think about the kind of person that writes a database that doesn't fsync your writes by default and relies on the page-cache over doing direct I/O when building a database.. doesn't really inspire confidence in the network stack, the query planner.. or well anything.

If anything it makes you insistent on not having ANYTHING to do with that sort of codebase.

Just replacing the storage engine might actually be good enough, but restoring my trust in the rest of the codebase is almost a forgone conclusion at this point.