In installations of Catalog which does not use xFlow or Service Point, there may continue to be events generated in Catalog that attempt to write to Search Server, but are not necessary. Search Server is a component that is utilised by xFlow and may be excused from Catalog operations if xFlow is not in use.
Service Catalog/xFlow/Service Point 17.3 and higher
Under Administration -> Event-Rule-Actions, go to Request Change and select the Rule "Sync Elastic search for request change rule" and disable action under it.