If my server was powered off, assuming all writes to disk succeeded, how many "confirmed" writes would I lose?
Redis: the lesser of 10k writes or 15 mins. See config
MongoDB: < 100ms (~30ms in practice) with default journaling enabled
RethinkDB: 0, see How does RethinkDB handle write durability?
CouchDB: 0, see setting
FoundationDB: 0. Claims to be ACID w/ keystore and SQL interface.
MySQL: ~0 (see comments)
The answer for every question is: "it depends". So what does it depend on, and what are the defaults. It's not that one is better, I just need to know the differences :-)
Hey, there's a guy who does a blog on this. Spoiler alert: every database sucks Note that some of the articles are about previously released versions.
With the default RethinkDB configuration, you won't lose any writes you've received responses for even if the server is restarted.