Rust has been taking steps in this direction for several years now, having first added pipelining via eager metadata emission in 2019: https://internals.rust-lang.org/t/evaluating-pipelined-rustc... . There have been several other steps in this process since then, e.g. working to make metadata less verbose, experimenting with different approaches to compression, etc. People have been eyeing making pipelining even more eager for a while now, as the submitter here noted a few days ago: https://news.ycombinator.com/item?id=49924257 , but there remain some decisions to be made regarding what to do when encountering errors in crates that were speculatively approved.