Hi Francis,

It is "to the same upstream server" that I care about. I would like to limit the request rate to the same upstream server.

The Scenarios is like:
10 requests at the same time to the same upstream server, the upstream server should only receive requests at rate 1r/m. Last few requests will be delayed or rejected. But for these last few requests, some of them can be served by cache, they should not be delayed/rejected.

Thanks,
Linna