Creating TTL Index

db.Carts.createIndex({ "ExpireAt": 1 },{ expireAfterSeconds: 0 , background: true});

Use Case

300 documents created at 1 second ExpireAt intervals.

Result

MongoDb expires 60 documents simultaneously in every minute. This is not a certain value cause of MongoDb doesn't guarentee expiration time. But, it is showing us MongoDb checks expiration time for every minute. So, 300 documents is expired in 5 minutes.