I had to opportunity to look at the code. I believe this should be compared against embedded hash database such as "kyoto cabinet, LevelDB, RocksDB" . They introduce a novel latch free hashtable that they say is faster than other in memory data structure.

They also introduce a new disk persistence system called HybridLog that combines in-place updates (in memory) and log-structured organization (on disk).

The interesting aspect of the HybridLog is that it act as a bufferpool but seem to work at the record level instead of working with pages like a B-tree buffer pool would or compressed block as levelDB block_cache does.