I haven’t kept track of how much traffic it brings to the whole website but I have some data about how much traffic it brings to the particular page that is trending on the HN front page: https://susam.net/from-web-feed-to-186850-hits.html
To summarise that post, it brought me about 95000 hits on the first day. That was a simple, static, standalone HTML page and the traffic was way below what Nginx can handle without breaking a sweat, so never had any trouble on the web server.
One year ago or so one of my posts ended up within the first few items of the home page and my blog got about 35K views over 2 days. The blog is hosted on a commercial platform and had no server issues.
I shared some stats here [0] from a front page Show HN. The data is a handful of years old, though.
[0] https://jeremyphelps.com/blog/from-idea-to-revenue-in-5-work...
10 years ago a post from @Bluehat for something we were working on* made #1 and generated about 7k clicks in 2 days.
Would suspect that number is much, much higher now.
* The Hacker Fair reverse job fair at the Hacker Dojo. #2 was "the CIA got hacked". Proud of that one.
30k unique visitors when my project hit the front page (not #1) a few weeks ago
10000 visitors an hour is less than 3 per second.
30000 visitors per day is 20 per minute.
With stats like that, break out an AWS XL and ensure your Lambdas are ready.
It's pretty common for sites to crash, especially those relying on some AI or GPU backed service.
Front page post got about 22k unique users over 2 days and never crashed (had CDN by the way).
A bit of a tangent but the big problem a friend of mine faced when he got on the front page was managing all the replies. It quickly gets difficult to figure out which comments are new and should be replied to.
There is a solution I am working on at the moment.
If you replace ycombinator in a url like: https://news.ycombinator.com/item?id=41816756
with gipety to get: https://news.gipety.com/item?id=41816756
you will get a page that remembers the comments currently displayed. On subsequent refreshes you will see any new comments highlighted in green.
It is not yet quite ready but if I get some positive feedback I might do a Show HN about it. (Would be ironic if too many people tried it and my site crashed ;)