upgraded mongodb version to 3.6.9 as https://jira.mongodb.org/browse/NODE-3309 is resolved now
(also see https://developer.mongodb.com/community/forums/t/nodejs-driver-bulk-write-performance-issue-after-upgrade-from-v3-6-6-to-v3-6-8/108113)
upgraded mongodb version to 3.6.9 as https://jira.mongodb.org/browse/NODE-3309 is resolved now
(also see https://developer.mongodb.com/community/forums/t/nodejs-driver-bulk-write-performance-issue-after-upgrade-from-v3-6-6-to-v3-6-8/108113)