I can recall plenty of times HN has been down.

it has already been facing some issues in the past couple weeks. e.g. the "front" page was broken randomly for past dates (like https://news.ycombinator.com/front?day=2025-05-30 or https://news.ycombinator.com/front?p=2)

as per their api documentation [1], it might be linked to firebase, which might explain this?

[1] https://github.com/HackerNews/API

the API has afaik nothing to do with HN itself, its a read-only copy for API users, not what backs the actual site.