The authLog structure is as follows :

{ "_id": NumberInt("0"), "la": ISODate("2020-12-04T01:25:54.054Z"), }

,

Then I use the following script operation：

for(var i = 0;i<2000;i++)

{ db.authLog.updateOne(\{"_id":i}

, {$currentDate: {"la":true}});
}

Then I discovered that it is possible that the update timestamp with a larger id is smaller than the update timestamp with a smaller id.E.g ：

{ "_id": NumberInt("100"), "la": ISODate("2020-12-04T01:25:54.054Z"), }

,

{ "_id": NumberInt("201"), "la": ISODate("2020-12-04T01:25:54.052Z"), }

.

Why does this happen and how to solve it?