Dumb question: is this running over Lightning? So it is Layer 3? Is it scalable?
CASHU: A VISION FOR A BITCOIN POWERED ECASH ECOSYSTEM – BITCOIN MAGAZINE
A look at the long term vision for an ecosystem of Cashu powered ecash mints, and how this can evolve to meet end users' needs balanced with security and functionality.
https://bitcoinmagazine.com/technical/cashu-a-vision-for-a-bitcoin-powered-ecash-ecosystem
Discussion
Settlement is via Lightning, but it's not a Layer 3 because it offers no cryptographic guarantees, it requires trust to the mint operator. And yes, it scales insanely well.