RethinkDB (YC S09): MySQL Storage Engine Built From The Ground Up For SSD
Database consistency problems require traditional databases to use complicated locks. Because RethinkDB data is always consistent, locking is unnecessary.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.