The Wasm module in question here was 2.6MB uncompressed, which we consider quite large. IIRC after enabling liftoff it took about 200ms to load. Smaller modules would be expected to load faster. We'd normally recommend doing some tree shaking to get the size down to something in the hundreds-of-kilobytes range, in which case the load time would be expected to be tens of milliseconds, comparable to a TLS handshake.

The developer who reported the problem here considered it to be fixed, and we haven't heard anyone complain about Wasm cold start times since then, so we haven't prioritized further optimizations for the time being. If current cold start times are a problem for you, though, then please let us know.