Set priority BEFORE the insert hits the DB — without an extra UPDATE.

01// Business Rule on 'incident'
02// When: ▢ ▢ ▢ ▢
03(function executeRule(current, previous) {
04  if (current.impact == 1 && current.urgency == 1) {
05    current.priority = 1;
06  }
07})(current, previous);