Rust on CF Workers is horrible. >10x performance hit (compared to JS) for a non-trivial web app, and it's not only a 10x performance hit but 10x the cost since they charge for CPU time, and that's where the extra time is going.

Realistically for a low traffic app it's fine, but it really makes you question how badly you want to be writing Rust.

As far as I can tell, the problem stems from the fact that CF Workers is still V8 - it's just a web browser as a server. A Rust app in this environment has to compile the whole stdlib and include it in the payload, whereas a JS app is just the JS you wrote (and the libs you pulled in). Then the JS gets to use V8's data structures and JSON parsing which is faster than the wasm-compiled Rust equivalents.

At least this is what I ran into when I tried a serious project on CF Workers with Rust. I tried going full Cloudflare but eventually migrated to AWS Lambda where the Rust code boots fast and runs natively.

I think performance takes a hit due to WASM, and I imagine pricing is worse at big qps numbers (where you can saturate instances), but I've found that deploying on CF workers is great for little-to-no devops burden. Scales up/down arbitrarily, pretty reasonable set of managed services, no cold start times to deal with, etc.

Only issue is that some of the managed services are still pretty half-baked, and introduce insane latency into things that should not be slow. KV checks/DB queries through their services can be double-to-triple digit ms latencies depending on configs.