I have a situation where a large batch of servers (X), on demand, need to request data from a smaller set of web servers (Y).
The worst case scenario is if all servers in X decide to fetch different requests to one server in Y. That would be X amount of connections, which could be a very large burst of traffic. The best case scenario is if 1 server in X hit 1 server in Y in tandem. Life does not work like this.
One idea to entertain is placing a proxy, similar to squid between X and Y. All of X servers can connect to this proxy, but would result in a few persistent (http keepalive) connections to Y. If The few were say, 3 or 4, then it would funnel. If we could then rate limit those connections and traffic decides to spike unusually high, we wouldn't hurt anyone but ourselves.