Yes we cache results for up to 12 hours. This means that if you run a report and then re-run it again within 12 hours you may get the cached results rather than us doing a new look-up. If your report does used the cache results it will process very fast, so this is a good indicator if the results are from the cache or new.
We cache results because rankings don’t change much within 12 hours and if they do it’s not a useful indicator of long term trends. It also means that if a report fails then we can re-run just the search terms which we did not get, so we don’t have to re-run the whole report again.