Alternatively, you could make a Nix flake that can generate an immutable microVM image based on Solo5, running a MirageOS unikernel that implements NAT traversal with UDP hole punching and relay fallback. This image can be deployed to Fly.io as a lightweight, autoscaling Firecracker VM with per-second billing. It boots in milliseconds and costs far less than Lambda.
Any reason to use lambda vs this cloud-agnostic approach? Maybe I am missing something. I guess per second vs per 100ms billing, but I can't imagine it ends up being cheaper with Lambda.