Can anyone explain why the npm registry still exists if it cannot guarantee that uploaded packages remain available? The current state makes it pretty useless as a reliable source te base software on because you never know if you're able to build it again in the future.
They should take a good hard look at NuGet, which does not allow packages to be deleted so builds are guaranteed to be reliable. Still doesn't hurt to locally cache packages with software such as Klondike.
They don't allow packages to be deleted. A bug or server issue or mistake caused this. This type of problem has occurred only once before. In general npm has been extremely reliable and performant.
They should take a good hard look at NuGet, which does not allow packages to be deleted so builds are guaranteed to be reliable. Still doesn't hurt to locally cache packages with software such as Klondike.