Fly.io Postgres cluster down for 3 days, no word from them about it

Fly works on a new and interesting platform paradigm by writing a lot of their software stack from scratch.

Unfortunately, such an approach is unlikely to produce the same stability you might be used to from other places.

I think their proxy could have been written from scratch. Some management, billing, API etc too but under the hood, it's all standard open source stuff like kvm, firecracker and such?