The equivalent of mirroring would be using a CDN. I understand that NixOS already does this through Fastly. The problem is that the base data is substantial (4

The equivalent of mirroring would be using a CDN. I understand that NixOS already does this through Fastly. The problem is that the base data is substantial (425 TiB) and expensive to store on S3. Just mirroring the base data would not change this. Some sort of way to distribute the 425 TiB among multiple hosts/etc might help, but seems like that would be really complicated to manage reliably—much harder than finding a new sponsor or moving off S3 to some more efficient alternative.