Maybe, i'm duplicating some existing theme (close this one if it's true) but i'm planning to work with high load web services and curios about best practices.
I have projects on Java and Grails. I'm doubt if Grails is right solution for high load service but Java (without any Hibernate or similar tools) can be used very well.
Anyway, what about best practices ? Does Java is good one or high load world is only for C++ and .NET technologies ?
Java can handle heavy loads. See http://www.jboss.org/netty/performance/20090607-asalihefendic.html which discuss how to have hundred thousand simultaneous comet connections open to a single server. Not bad.
Note, that this kind of scalability does not come out of nowhere. Your application must be well written in the first place and carefully integrated with the web container. You should therefore set up a testing scenario which can put high load on your web application to see how it behaves. JMeter can help doing that.