> If you want to rely on SQL to do all the locking for you this usually doesn't scale. I suspect you have a mis-adjusted notion of "usually". "Usually", as in,

> If you want to rely on SQL to do all the locking for you this usually doesn't scale. I suspect you have a mis-adjusted notion of "usually". "Usually", as in, for the majority of systems designed and in-use in the world, a well tuned, reliable RDBMS will be able to do this absolutely fine. The scale of systems that the world needs vs the quantity of them is an extremely long tailed curve.