Shopify lets you run [wasm as part of their infra]( They call them "Discount Apps" for some reason, and the technology is [Shopify 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]( [Blog post about it](