Ways to achieve this when developing your applications:
One is to add logic to your application to store files on a cloud object storage system like Amazon S3.
Another is to create volumes with a driver that supports writing files to an external storage system like NFS or Amazon S3.
Volume drivers allow you to abstract the underlying storage system from the application logic. For example, if your services use a volume with an NFS driver, you can update the services to use a different driver, as an example to store data in the cloud, without changing the application logic.