Aside from some scaling issues, it still is a great solution for having real-time insight into the performance of Varnish and the cache. We even went as far as

Aside from some scaling issues, it still is a great solution for having real-time insight into the performance of Varnish and the cache. We even went as far as writing a Golang version of the VCS server to better handle some of the scaling challenges. I don’t remember the exact library that we are using to call into ZeroMQ, but the CGO overhead was minimal.