Bitbucket Cloud is backed up regularly by Atlassian. Atlassian has the ability to restore from its backups but otherwise you should not have to worry.
If you are still concerned, Git is a Distributed Version Control System, you could always just sync your repository to other locations to back it up.
You can read about this more here: https://confluence.atlassian.com/pages/viewpage.action?pageId=288658413
I hope that helps.
Like Massaioli, I'll assume you're running Git, but the same advice applies to folks running Mercurial:
Robert Massaioli 
> Git is a Distributed Version Control System, [so] you could always just sync your repository to other locations to back it up.
Better yet, remember that
1. Your Cloud repo is just a remote of your local repo, which is just part of your local work directory, which is (wait for it ...) on your local file system! which you should be backing up regularly! if you value your sanity.
2. Your local repo is only part of your local work dir. Your local work dir(s) should contain all code (wait for it ...) on which you are working. Your repos (local or remote) are not backups for your local work! They should only contain work that has been finished (e.g., tested). So you still need to backup your local work dir--i.e., your local filesystem--even if you have a remote repo.
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