It's not a choice that's guaranteed to suit your use case, but storing a time series as a large set of rows is not performant. Perhaps I should have mentioned that our time series data is "write once": we record and store it, but it doesn't get altered. And the time series are all sent to the browser, which does the displaying, filtering and analyzing, so there's no point in processing (our particular) time series in SQL, if that were even feasible. So, basically, because it is good enough, and better than the available alternatives.