Shopify lets you run [wasm as part of their
infra](https://apps.shopify.com/collections/functions-discounts). They call them
"Discount Apps" for some reason, and the technology is [Shopify
Functions](https://shopify.dev/docs/apps/functions).
> Shopify Functions allow developers to customize the backend logic of Shopify.
This guide introduces how Shopify Functions work and the benefits of using
Shopify Functions.
They us [wasi](/wasi/).
> The module must consume a JSON-formatted string via stdin and produce a
JSON-formatted string on stdout.
They have a 5ms timeout, and 256KB size limit.
> We’re exploring a gas-like approach as a machine- and situation-independent
measurement to give developers confidence that their function is fast
enough.
They use quickjs to run JavaScript in WASM. And they have built
[Javy](https://github.com/Shopify/javy). [Blog post about
it](https://shopify.engineering/javascript-in-webassembly-for-shopify-functions).