Which site? My blog? The blog is still on Heroku, and it sounds like it was overloaded for a while there. I just upped the number of dynos, so it should be fine.
I don't have any indication that soundslice.com (which is the site I'm hosting on AWS) was returning any 500s, but if it was, please let me know.
I don't have a definitive answer for the blog, to be honest. I just add four more dynos (to bring it up to five total) and it seems to be fine. I figure it's only for a few hours, so I can be sloppy about it without needing to worry about huge costs. Wish I could be more scientific about it!
As for the number of dynos when Soundslice was on the Reddit homepage, I think was using 10 at that point, but, again, it was a totally non-scientific thing. 10 did the job, but fewer dynos might have been just as fine.
I don't have any indication that soundslice.com (which is the site I'm hosting on AWS) was returning any 500s, but if it was, please let me know.