SQL DBs scale just as well as NoSQL and in the exact same ways: read only clones, sharding, federation, etc. YouTube runs on MySQL in case you're worried about

SQL DBs scale just as well as NoSQL and in the exact same ways: read only clones, sharding, federation, etc. YouTube runs on MySQL in case you're worried about scaling. It may be a tad easier with something like Mongo but it's not hard with MySQL. IMO, NoSQL is attractive mostly because it's schemaless. You need to change up your model all the time, or handle arbitrary datasets but still query them? NoSQL may be the right tool for the job.