A well configured small / medium instance should easily handle 100 requests/second. My test PHP setup on micro instances serves 1000 requests/second before any signs of slowdown. [1]
Every application is different and has different requirements. I know absolutely knowing about the original author's application so I can't comment on any specifics. But just because your "test PHP setup" can handle X amount of r/s does not suggest that any other application should be able to do the same.
