Proxy-wasm is a standard that can be used to extend the features of proxies like Envoy to do things that can't be solved with pure configuration. The standard is rather young and has some very rough edges, both in the SDKs as well as languages and getting it loaded in a running Istio setup. In this talk, John talks about the experience going from nothing to a production setup and all the mistakes and faults that were discovered along the way (so you don't have to make them).