You're right, I failed to mention disaster recovery– it was something we looked at, its just been awhile since we went through the evaluation process, so I've forgotten a few things. We actually liked Cassandra for DR scenarios – the snapshot functionality makes backups relatively straight forward, plus multi-DC support will make operational continuity in the case of losing a whole DC a possibility.

If we're going to have to slow the system down, we'd rather use the standard interface, because that means the bulk loading doubles as a load test and the tools we build for it can be re-used for normal operations.