If you've tried H2 Database, the pure-Java, embedded, in-memory, in-process Database that StreamCruncher ships with, you'd be amazed at how much work has gone into its development. Well, it supports other modes as well, but this mode is the default/recommended setting in SC.

Thomas Mueller, the guy who owns/develops H2 was also the same chap who developed HSQL DB before someone else took over the responsibility from him. And now, HSQL DB is part of OpenOffice's Base application - Sun's answer to MS Access. That's really something.

H2 is turning out into a full fledged DB, what with its Spatial indexing, support for large (several GB) Database sizes, support for all sorts of twisted but very handy SQL syntax.. From StreamCruncher's point of view, the embedded mode in H2 is highly suitable. The less latency at the DB, the better. Last time I spoke to Thomas (over email), H2 did not have any support for concurrency. H2 was thread-safe, but didn't allow concurrent operations - just like HSQL DB. I hope he spends some more time removing that major bottleneck. Atleast, Table-level locking/concurrency will be very good. HSQL DB on the other hand locks the whole Database, which is ughh..

In any case, I admire the effort that he has put into H2.

PS: It's "relocation time" for me. I'm moving out of Singapore after having spent a 1 year and almost 10 months doing Consulting work. Nice little city, Singapore.