Run the following steps in the mongosh: use test-db db.createCollection( 'users' ) db.users.createIndex({ 'username' : 1 }, { unique: 1 }) db.users.insert({ "username" : "LDAP" }) db.users.insert({ "username" : "ldap" }) var bulk = db.users.initializeUnorderedBulkOp() bulk.find({ "username" : "ldap" }).collation({ "locale" : "en" , "strength" :2}).upsert().updateOne({ "$set" :{ "username" : "ldap" }}) bulk.execute()