In case you host MongoDB externally, the backups need to be managed by you. You can use these helpful articles from MongoDB that explains all possible backup options.
Kendis supports MongoDB version 3.6 and 4.0
How to take backup for MongoDB v 3.6: https://docs.mongodb.com/v3.6/reference/program/mongodump/
How to take backup for MongoDB v 4.0:
In case you would need to restore these backups, you would need to use "mongorestore" , more info at https://docs.mongodb.com/manual/reference/program/mongorestore/