The Execute Code, Execute Function and Execute Tool endpoints are all backed by a set of runtime engines. Every time you run code, it runs using exactly one of these engines.

Unless you’ve created a Custom Runtime, your code runs using the default WASI engine. When you create a custom runtime, the flags on your account determine which engine the custom runtime uses.

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WASI

The default runtime engine is WASI, which is a server-side interface for WebAssembly. This engine is extremely performant but has some limitations, notably limited support for third-party dependencies.

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microVM

When you run code in a Custom Runtime for Python or JavaScript, by default that code runs using our microVM runtime engine. This engine is more flexible than WASI but isn’t quite as fast.

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V8 (beta)

For JavaScript specifically, we are devleloping a new runtime engine based on V8. This engine offers the flexibility of our microVM engine but with better performance. If you’re interested in trying it out, please get in touch.