Its a core dependency for rate limiting, traffic shaping, fail over detection. Its cluster subsystem is super convenient for local LLM calls too. We'll write up a blog on the lessons because there were many. For example, for intelligent routing decisions we can't create an upstream connection to a cluster based on route paths or host - Envoy forces a more static binding. This doesn't work when you are making decisions about a prompt and have to inject more dynamic flow control.