It is pure optimization - they said it gives them a performance boost and smooths things out. In their "flat-file" setup though - they are deliberately configu

It is pure optimization - they said it gives them a performance boost and smooths things out. In their "flat-file" setup though - they are deliberately configured so that, should varnish fail (which was one of their concerns) - they don't actually need it - they could just have haproxy immediateley start hitting the apache servers directly.