Why would I want to replace my reliance on them with reliance on Amazon or another cloud provider?
I'd rather control the whole stack, even if it means deploying my own hardware to one or more redundant, off-site locations.
Edit: Are there robust, open source, self-hosted, S3-compliant engines out there reliable and performant enough to be the backend for this?
The old open source version of Minio still works
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There’s local file system as an option for storage provider.
But then you still need a bazillion dependencies and a db just to manage files already on your filesystem.