Actually no, it's load. We have 80 million page hits a day and each of these can run 10-20 queries on a 2TiB dataset. We're not a small outfit. We use Nhiberna

Actually no, it's load. We have 80 million page hits a day and each of these can run 10-20 queries on a 2TiB dataset. We're not a small outfit. We use Nhibernate profiler to check our SQL output and all of our queries and make sure we're not doing anything stupid. We know how to use relational databases, but it's expensive and hard representing our problem domain with them so an OO system is better. We optimise later by switching the engine out to something cheaper. At least we CAN do this with an ORM abstraction without too much pain. After all, premature optimisation is the root of all evil isn't it?