A sound strategy for a backup solution would be to have atleast two recoverable backups incase of a meltdown. And they do occur.
We started off with a single backup solution on Digital Ocean's backup solution. We then further expanded that with daily backups of database and essential files to Amazon S3. We further introduced Google Nearline Storage to the mix that takes all our S3 buckets on a daily basis and backs it up to Nearline.
The latest addition has been Google Coldline where we archive Nearline buckets after 120 days in Nearline.
Backups are retained for 60 days in S3, 120 days in Nearline, and 365 days in Coldline. All base code is hosted on GitHub.