From the looks of it, Go/Rust cold starts are almost completely CPU bound, so you see the near perfect scaling there. Meanwhile Python I'd guess is mostly io bo

From the looks of it, Go/Rust cold starts are almost completely CPU bound, so you see the near perfect scaling there. Meanwhile Python I'd guess is mostly io bound, which doesn't scale. That kinda makes sense as Go/Rust compile down to single executable while Python loads lots of libraries from disk. For Rust, I suspect spinning up Tokio and the rest of async runtime might be making cold starts worse. But that's purely speculation. The python lambda is good old-fashioned sync io. Another difference is that Rust lambda initializes a logger, while Python one doesn't. That might add some milliseconds too to the startup.