Earlier quoted context omitted.
Or use ToroDB ( http://www.torodb.com ) that speaks the MongoDB protocol but stores the data relationally, in PostgreSQL. Directly. No ETL, no mosql required :) (ToroDB developer here)
hey - this looks interesting. Quick question: why did you build it in Java rather than as a Postgresql extension - like mongres [1] or mogloid [2] ? [1] https://github.com/umitanuki/mongres [2] https://github.com/JerrySievert/mongolike
I contrast, PostgreSQL extensions need C, which doesn't have these advantages and becomes less productive.
But even more importantly: we don't want to tie it, as much as possible, to PostgreSQL. Maybe, tomorrow, ToroDB would run on other RDBMs :)
If run locally, there's barely performance hit. And it also enables you to run it remotely.