We actually do have a persistent `stevedore` in Varnish Cache, but we have marked it "deprecated" because it did not live up to expectations, but we keep it aro

We actually do have a persistent `stevedore` in Varnish Cache, but we have marked it "deprecated" because it did not live up to expectations, but we keep it around to keep the internal API's honest. Redesigning that code has not bubbled up to the top of my TODO list yet, and shows now signs of doing so. But if you need persistence, there is a commercial version of Varnish which has it, but I have not been involved in that.