Lukas Smith responded on Twitter to a posting of mine I made on this blog about the possibility of having a precompiled bootstrap in PHP that would allow large sections of bootstrapping code to be bypassed, including autoloading, class definitions and certain objects.
His tweet linked to the link above which solves the problem, but in a different way. It requires a middle layer that needs to be running to process these requests. I believe that I have thought about doing something similar using ESI locally which did not work out so well since Varnish processed ESI requests synchronously.
I have not played with this library and I would prefer a solution that is closer to the engine and doesn’t add another layer. That said, this looks like an interesting project that seems worth taking a look at.