The relationship between xDS filter config and Wasm execution instances is rather confusing, which makes it hard to provide guidance on scaling (e.g. with respect to heap/stack size per instance). In the simplest case of two identical listeners referring to the same identical WasmFilter config, we see the following:

• _on start is only executed once per execution instance, but there are many temporary instances created during configuration, for canary I presume.
• on_configure is called twice on the same instance, with the same parameters - this happens even when listeners have distinct listener metadata.
• on_request_headers is called on the same instance per each request regardless of the listener.