RethinkDB (YC S09): MySQL Storage Engine Built From The Ground Up For SSD
<i>Database consistency problems require traditional databases to use complicated locks. Because RethinkDB data is always consistent, locking is unnecessary.</i><p>You may not use locking for concurrency control (plenty of "traditional DBs" don't, either), but you still need some sort of concurrency control scheme -- just using append-only/log-structured storage doesn't make CC free. I'd be curious to hear how you guys are doing this.