[kamjam]

What happens when something like nuget.org/npm/other equivalents that you have a dependency on from your code/build system go down?

Unless you are self-hosting everything then there is a reliance on 3rd parties. Even when you self-host, you have a dependency on your IT team for maintenance - 100% uptime is impossible for anyone, servers sometimes need to undergo routine maintenance or an upgrade. Yes, I understand the difference being it's on your own timeframe, but often it's just been one of those things.

Even with these small outages, would be interested if anyone is able to keep higher uptime themselves.

[koolba]

Exactly. For some build systems (ex: Maven or NPM) you can have a local proxy the mitigate a lot of this. It also has the advantage of having a fixed (hopefully validated!) set of dependencies instead of pulling it whatever wild-wild-west change there is in the latest version of something. It also insulates you from the historical changes.