In one case I cited elsewhere in the comments, an engineer had called ramda.uniq on an array of nested objects which was occasionally very large. When calling into external packages, I don't think we have as much control over yielding to the event loop, but I could be wrong. I know that there are some JSON/regex libraries that give you some protection on this front.

I agree that it would be nice if all developers were infallible – I'm reminded of a friend describing their company, where "we don't write tests because we all write good code". At a certain point, you have to look for processes – linters, monitoring, testing, language choices [1] – where people can't shoot themselves in the foot. (Code reviews being only moderately less fallible than a single engineer.) It's not enough to just say "be better" whenever bad code is written.

I think when the decision was made (years ago) to handle a single request per container, they couldn't find such a process to prevent event loop blockages, other than migrating an already-large codebase away from Node. As others have pointed out, maybe such a migration is necessary – after all, event loop blockages are still an inherent risk because of how Node works. It's just a lower risk than it was a year or two ago, because we've significantly improved our usage of the event loop, and also have tooling in place to catch blockages before they become an issue.

[1] https://news.ycombinator.com/item?id=18564643