I'm not familiar with scaling Java, but I've worked with the language itself on Android. What makes it so great for scalability as opposed to something like Ruby?
If you are using Rails, the database is the problem 99% of the time, not Ruby. MySQL can easily* be scaled / denormalised / sharded then if you need to you can just horizontally scale your app servers.
If you are using Rails, the database is the problem 99% of the time, not Ruby. MySQL can easily* be scaled / denormalised / sharded then if you need to you can just horizontally scale your app servers.
(*As easy as MySQL can. It isn't a black magic though, there is plenty of documentation, e.g. http://www.mysqlperformanceblog.com/)