This, and most discussions about this seem to focus on situations where a human (browser) is on one side of the connection and the request flow is strait throug

This, and most discussions about this seem to focus on situations where a human (browser) is on one side of the connection and the request flow is strait through. In complex backed systems you have trees of requests to satisfy one browser request. Often the requests are small RPC type requests and even a few ms is important.