In Java. For a low-level in-process library that most people link in to their actual app Java is completely unsuitable. Not quite sure how this replaces most of the BDB use-cases, but if you are going to run in another process then there are a whole host of options to consider. Tupl looks pretty interesting and it would be fun to have a reason to play with it, but this does not handle any of the cases where I turn to BDB.