We built a faster WASM-bindgen (2.5×) for high-frequency JavaScript<–>Rust calls

A few years back we tried moving our in-memory database engine from Typescript to Rust but found the prototype gains were pretty much deleted by wasm-bindgen because of the high call frequency in our setting.

Moving more of our stack into Rust wasn't viable, so we shelved the project and focused on other areas.

Turns out this is a pretty common experience.

Now we're trying again, but this time with our own binding protocol. It’s 2.5× faster at the boundary, but more importantly, it shifts the break-even point dramatically. Offloading to WASM becomes viable at much smaller data sizes (e.g. ~100 elements), enabling cases that weren’t previously worth it — including ours.

The only trade off is significantly worse DX - the bindings are manual and more verbose, but I'm sure someone could solve this with codegen/macros on either side. For now we're focused on performance.

It's pretty much neck and neck between our Rust and Zig implementations so take your pick.