Ah OK, after reading their docs I see they've changed what "slots" used to mean in Dremel (internal version of BQ). It used to be that slots _guaranteed_ capacity, but did not limit it. Meaning that you could rely on having a certain number of workers in the cluster when you issue a query, but if Dremel had more it'd give you all it's got. Obviously this is not viable when people have to pay per terabyte read, because a ton can be read.

What they have now strikes me as an even better solution to the problem of bankrupting someone with a query IMO. Not sure how pricing compares to redshift et al, but pricing is the easiest thing for Google to change.

Slots don't control how much data you consume, your query does.

If you need to read a terabyte of data to answer your query then more slots only gets it done faster.