From the engineering side, this is probably driven by cost. What’s the cost of a page-view? Hopefully you’ve got a scalable architecture so you can say something like:

It’ll cost us $300/month to push 20 pages/second, plus ops concerns. If we want to push 40 pages/second, that’ll cost us $600/month because we’ll need to add another box.

I don’t think I’ve got a rule of thumb in general. Performance varies from application to application so much that it’s hard to say. OSE is pretty data intensive: one report issues five or six API requests for a few thousand rows of data, hits the database a handful of times, and queues up other work for background processing. On the other hand, there are plenty of benchmarks that suggest a naive ruby app that does basically nothing can do ~500 page-views/second on low-end commodity hardware.

I guess there you go: per box you should get at least 10 or 20 page-views/second at the low-end. But it’s unrealistic to expect 500 or more page-views/second from any real app on the kind of hardware you’re likely to see in production.

Cheers,
Chris