Using MongoDB to implement tree structures has some advantages, but as it lacks features that traditional RDBMSes have (like table locking and transactions), it is easy to create race conditions during simultanous operations. This is a pretty generic problem and I hope we can emphasize common problems and best practices on the implementation of thread-safe tree tables here.
Felix von Leitner's original paper on BSD and Linux io performance.
Dan Kegel's updated paper on high-performance network io programming on Unix.
