Caddy does (some of) that too actually. It has a live config API and support for clusters and synchronized configs and TLS cert management. It can also get the

Caddy does (some of) that too actually. It has a live config API and support for clusters and synchronized configs and TLS cert management. It can also get the proxy upstreams dynamically at request-time through various modules. Some of the biggest deployments program/automate Caddy configs using APIs and multi-region infrastructure. But where Envoy shines, it really shines.