We made an Envoy Proxy playground [0] so we could test out our Envoy configs directly in the browser. This is based on Julia's work with Nginx Playround. [1] We forked that repo and added more Envoy to it. [2] Check it out!
[0] - Envoy is a popular programmable proxy similar to Nginx or HAProxy that is popular with cloud-native setups: https://www.envoyproxy.io