Varnish will actually hold those 100 connections open while it dispatches 1 single request to the backend. When that request returns (assuming the cache control

Varnish will actually hold those 100 connections open while it dispatches 1 single request to the backend. When that request returns (assuming the cache control headers allow it), it will serve that one response to all 100 requestors. It's a very powerfull tool for anything that's even slightly cachable.