IMO it’s fine to just make a post about it in one of the larger communities that seems appropriate. Now is exactly the time for us to promote one another! And Lemmy doesn’t have an algorithm, so you’re going to have to do some leg work to get the word out. I think people will be appreciative and understanding of that, I would be.

spy on all the traffic

That’s…not how things work. Everyone has their philosophical opinions so I won’t attempt to argue the point, but if you want to handle scale and distribution, you’re going to have to start thinking differently, otherwise you’re going to fail when load starts to really increase.

You could configure something like a Cloudflare worker to throw up a page directing users elsewhere whenever healthchecks failed.