Yes, there is a throttling process in place if > 500 requests per minute by a single user or against a single realm.
You had over 600 requests during the one minute period.
Looks like almost all (all except 32 requests) were individual customer queries… all different customer record ids. Is there a way you can make a single customer list query, filtered if necessary, to get a bunch of customer records in a single request and reduce the number of calls you are making.