I'm betting this is on the front page today (as opposed to any other day; Juice is very neat and doesn't need us to hype it) because of our Sprites post, which goes into some detail about how we use Juice (for the time being; I'm not sure if we'll keep it this way).

The TL;DR relevant to your comment is: we tore out a lot of the metadata stuff, and our metadata storage is SQLite + Litestream.io, which gives us fast local read/write, enough systemwide atomicity (all atomicity in our setting runs asymptotically against "someone could just cut the power at any moment"), and preserves "durably stored to object storage".