Seems like Fly.io Machines are trying to reimplement Kata Containers with the Firecracker backend [0], but also abstracting away the host hypervisor machine infrastructure.

Kata has a guest image and guest agent to run multiple isolated containers [1].

[0] https://katacontainers.io/

[1] https://github.com/kata-containers/kata-containers/blob/main...

It should discuss what you don’t get compared to the standard behaviors of Kubernetes.

The problem is not the need to bin-pack, the problem is completeness. Sidecars and multiple containers are used for logging, backups, etc. Not to mention that if you grab a manifest or chart for an app, it is going to have pods with multiple containers (whether that's strictly needed or not), and those won't work on fly.io.

This is a critical feature available in every Kubernetes offering, and as such people rely on it. Trying to say that maybe you can do without is missing the forest for the trees.

Like saying that your C compiler doesn't need arrays because it has pointers: sure, maybe, but now good luck compiling any existing code. Maybe don't call it a C compiler if no C program will work on it unmodified.