I think you didn't read through to this part of my comment:
> I think the most important thing the author learned is that failing to add an index can cost this much money before you notice.
> Ideally the author and/or the vendor will also brainstorm ways to make these errors obvious before the high bill. Load testing with realistic data is one way (though people talk about load testing a lot more than they actually do it). Another would be watching for abrupt changes in the operations the billing is based on.
> I think the most important thing the author learned is that failing to add an index can cost this much money before you notice.
> Ideally the author and/or the vendor will also brainstorm ways to make these errors obvious before the high bill. Load testing with realistic data is one way (though people talk about load testing a lot more than they actually do it). Another would be watching for abrupt changes in the operations the billing is based on.