This is something I’ve learned in my 16 years running IT Operations:
If you want to ensure you know your environment, control your dependencies versions. Enforce versions. Do not use “latest” without testing it.
Even if you have automated tests, even if you have a CI/CD, even if you have 100% of coverage: You can’t ensure something won’t brake.
You can test your entire code base and monitor all your services but you can’t test the entire realms of possibilities in the world!
Things can brake in a unimaginable number of ways. That is why even Google and Facebook have outages once in while.