In order to see how much time your mongoDB slave is behind the primary node:

rs0:SECONDARY> db.printSlaveReplicationInfo()
 source: mongo.mongo.com:27017
     syncedTo: Mon Nov 12 2018 06:33:40 GMT+0000 (UTC)
     -4 secs (0 hrs) behind the primary

#mongodb #mongo #slave #printSlaveReplicationInfo #replica #replication

In MongoDB you can compare one field to another using $expr:

db.users.find({ $expr: { $eq: ["$created_at", "$updated_at"] } })

Here we get users that their updated_at field is equal to created_at field, here it means that user has not yet updated his profile.

#mongodb #mongo #expr #find

MongoDB server Load Average: 0.5 (It can reach 16)
Database Size: 100GB (It is compressed in MySQL it reaches 300 GB in size!)
Req/Sec: 500

Our server seems hungry for more requests and more data.

#mongodb #mongo #awesomeness