Same as for almost every bug I think: the dev in question hadn't considered that the input could be bad in the way that it turned out to be. Maybe they were new, or maybe they hadn't slept much because of a newborn baby, or maybe they thought it was a reasonable assumption that there would never be more than 200 ML features in the array in question. I don't think this developer will ever make the same mistake again at least.
Let those who have never written a bug before cast the first stone.
> Maybe they were new, or maybe they hadn't slept much because of a newborn baby
Reminds me of House of Dynamite, the movie about nuclear apocalypse that really revolves around these very human factors. This outage is a perfect example of why relying on anything humans have built is risky, which includes the entire nuclear apparatus. “I don’t understand why X wasn’t built in such a way that wouldn’t mean we live in an underground bunker now” is the sentence that comes to mind.
I don't think this is an error originating from a single human. At CF scale I'd expect that multiple humans saw that code and gave it a pass.
Rust or not, but an experienced dev could have seen this can lead to issues. Panicking without restoring a healthy state is just not an option in this case. They *know* that.
I guess you are right, likely a social issue, but certainly not a single exhausted parent.
Let those who have never written a bug before cast the first stone.