Object/relational impedance mismatch is solved by a new class of database built on immutability. If the storage segments are immutable (like git), the query process can be moved out of the central transaction processor and into the horizontally scalable application process (like git). When query engine is embedded in the application process, all the latency and network round trips drop out (like git), which solves in one fell swoop all the intractable optimization problems that ORMs attempt (and fail) to abstract away. One such database is http://www.datomic.com/

edit: these databases are relational, acid and competitive with postgres. Strong consistency is achieved by threading through a notion of time (like git)

i wrote about it on reddit once, here: https://twitter.com/dustingetz/status/690374292027117568