Finally, we are beginning to see some real back end applications of wasm apart from envoy proxy. This seems very similar to apache storm [1], where users can define UDFs (user defined functions) on their streams.

Although, I dont understand whats the value add of wasm (apart from security) if the user still has to write code in Rust -> wasm. Why not just execute in rust alone?

[1] https://storm.apache.org/

Until now, container was only way to provide isolation boundary which as process. With WASM, we can provide very fine level isolation and execution control.

You can compile almost any language to WASM not just Rust. For example, Python, Go, Javascript: https://github.com/appcypher/awesome-wasm-langs.