a. PolarDB is based on a similar idea. https://www.cs.utah.edu/~lifeifei/papers/polardbserverless-s.... This paper describes it. The biggest difference that I see glancing through the paper is that we really integrated S3 into the storage. In Neon architecture branches, backups, checkpoint are all the same thing and instant to run. This simplifies a good amount of database management AND deliver on better costs. S3 is cheap.
b. Neon doesn't need a special filesystem. Neon storage is in a way a filesystem, however it doesn't expose filesystem API. It's a key value store - serves 8k pages to Postgres and a consensus - update API to the key value store. Pages are organized in LSM trees and background processes put layers of the LSM trees to S3.
c. The cols start is 2sec right now. There is a dependency on K8S. Bare metal implementation will require new code to orchestrate starts and stops.