It would be interesting to know how much traffic we need to estimate before submitting a website here, so creators can be prepared and warned.
Stuff I've had on the front page before has received somewhere between 300-2000 simultaneous visitors, and between 10,000-80,000 total visits.
My experience has been pretty close to that; if I hit #1 then the peak is usually around 500-1000 simultaneous visitors according to Google Analytics, and the total number of visits is around 30-40k. Being around the middle of the front page is around 200-300 simultaneous visitors, and a correspondingly lower number of total visits; I don't know if I've ever had less than 10k total visits from a front page link.
Another project that posted their traffic numbers it got from being on the HN frontpage. Looks like 300 sessions/hour, 2000 total for them. https://news.ycombinator.com/item?id=10072660
I got 8.5k in the first day of a post here, which was less popular than this post (I saw something like 150 sessions/minute when I peaked at #6)
I'll report back once this is done. It's back up.
We got around 18k hits.
That was bittersweet. Was on a small digital ocean droplet. Wasn't expecting such a large response, so I'm really happy. I've upgraded the droplet so hopefully everything continues to work now.