Good article. Firecracker is something that has definitely piqued my interest when it comes to quickly spinning up a throwaway environment to use for either development or CI. I run a CI platform [1], which currently uses QEMU for the build environments (Docker is also supported but currently disabled on the hosted offering), startup times are ok, but having a boot time of 1-2s is definitely highly appealing. I will have to investigate Firecracker further to see if I could incorporate this into what I'm doing.
Julia Evans has also written about Firecracker in the past too [2][3].
[1] - https://about.djinn-ci.com
[2] - https://jvns.ca/blog/2021/01/23/firecracker--start-a-vm-in-l...