Can Zoho Reports really handle millions of rows?

Can Zoho Reports really handle millions of rows?

Zoho Reports claim that it can handle millions of rows. I frequently encounter the error " Sorry, refresh operation of the underlying query table was aborted, as processing time exceeded the allowed time limit. Please try after some time. Contact support, if the issue persists"  on trying to view a query table which joins two tables with just 16,554 and 16,550 rows. The query table just joins the two tables on four columns which have all been indexed.

Not sure what to believe- what I experience or what Zoho claims and what to expect when my database grows