I wonder what source language they are using that will be compiled to WebAssembly. I also wonder how they built their FaaS infrastructure. A possibility is that they used the open source Firecracker (written in Rust) which powers AWS Lambda.

"A key reason behind Amex's adoption of WebAssembly is that WebAssembly demonstrated superior performance metrics compared to containers."

Wasm faster than containers? I guess they mean under there specific circumstances. Rust or C on a Linux container running machine code should definitely be faster than Wasm bytecode.