To schedule backup mongodb to AWS S3 could be done extremely easy in any docker pipeline, here is an example using DroneCI docker pipeline and cronjob feature. The complete code example could be found here: https://github.com/Asing1001/mongodb-s3-backup.
- Create .drone.jsonnetfile using docker pipeline
- Use mongodumpin step1 to create archive
- Upload the archive by - s3 pluginin step2- 1 
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 39- local backupLocation = 'mongo-archive.gz'; 
 [{
 kind: 'pipeline',
 name: 'default',
 steps: [
 {
 name: 'mongodump',
 image: 'mongo:3.6.5',
 environment: {
 DB_URI: {
 from_secret: 'db_uri'
 },
 },
 commands: [
 'mongodump --gzip --uri="$DB_URI" --archive=' + backupLocation,
 ],
 },
 {
 name: 'upload',
 image: 'plugins/s3',
 settings: {
 bucket: 'mongo-backup',
 access_key: {
 from_secret: 'aws_access_key_id',
 },
 secret_key: {
 from_secret: 'aws_secret_access_key',
 },
 source: backupLocation,
 target: '/',
 },
 },
 ],
 trigger: {
 event: ['cron', 'push'],
 branch: 'master'
 },
 }]
- Activate the project in DroneCI and fill up variables - aws_access_key_id,- aws_secret_access_key,- db_uri
- Setup Cron jobs in Drone project’s settings  
- Push the repository and verify the job :)