[solatic]

Nexus OSS can't be clustered / put in a highly-available install, which is a paid feature for Nexus.

To ensure that you're actually deriving benefit from your Nexus install, you have to block outbound connections to the NPM public registry from your CI build agents (if you don't firewall it off, you don't want to wake up one day and find that both origin and the proxy are erroring because your proxy never actually cached anything and you never tested tested your proxy... right?), with only the Nexus installation permitted to make such outbound connections. And as bad as NPM may be, there are real maintenance costs to running your own Nexus install (not least of which, managing updates that will take Nexus down and communicating them with your dev team so that CI builds which error out when Nexus is down can be restarted when it goes back up), and thinking that you can do better than NPM is hubris. Running a private Nexus OSS install for the purpose of trying to increase availability for low cost (not zero - you still have to pay the infrastructure costs) is usually a false economy.

If you work for a company with enough operations and infrastructure resources that adding a clustered install is trivial, then you probably have enough resources to pay for an Artifactory license.

TL:DR - NPM has its faults but it's still probably de-facto both more available and better updated than taking on the responsibility of running a proxy unless you have mature ops/infra teams