Thanks!

stat doesn’t pull the file contents from S3; it only accesses the metadata tree, which is usually cached.

I haven’t benchmarked Borg or Restic specifically. Sequential writes can comfortably reach several Gbit/s. For follow-up runs, if they only stat unchanged files, that should stay entirely in metadata.

The default Redis/Valkey configuration should work fine for conditional_put. NFSv4 is unlikely for now. It would add a lot of surface area, and I’m pretty happy with where the 9P extensions are today.