When should I use a WASI based WebAssembly module instead of a native C++ addon?

Weighs trade offs between speed, safety, and interoperability.

WebAssembly System Interface (WASI) in Node.js (v20+ and LTS) enables sandboxed WASM modules running directly in JavaScript, providing a safer and more portable alternative to traditional C++ addons : • Use WASI when: o You need strong cross-platform sandboxing (e.g. running untrusted extensions). o You want automatic streaming and retry logic built into WASM runtimes. o You prioritize portability: the same WASM runs in Next.js, Node.js, and edge runtimes. • Use native C++ when: o You require maximum raw CPU-side performance (since native C++ still out performs WASM SIMD by ~10–15 % in benchmarks). o You rely on deeply native APIs or libraries not yet available via FFI or WASI. o Binary size matters at install time (WASI runtime and module files tend to be larger). Most modern Node.js use cases benefit from WASM with WASI unless you require deep native integration or absolute peak performance.