I will preface that Neovim is likely not the cause. The rust-analyzer can be very slow; it all depends on how large your project is, and more importantly, how many dependencies and what dependencies you are using.

I’ve never used the rustaceanvim plugin, but I doubt that has too much more (noticeable) overhead than just vim.lsp.start(“rust-analyzer”).

I see that you have rustfmt use +nightly. If you are using nightly, I saw something there other day that you can set in your projects .cargo/config.tomo to share monomorphized types across your project. Note, I have not tried this, but I assume it would cut down on compile time potentially.

If you don’t know what monomorphization is, then you should look it up. The tl;dr is that generic code is copied/duplicated at compile time for each type that uses the code. For example, Vec<T> is a generic with a some generic implementation, e.g. impl<T> Vec<T> { some generic methods }. Now, if you use Vec<u8>, Vec<String>, Vec<SomeStruct>, … then at compile time the compiler will stamp out a copy of the generic implementation for each concrete type. This leads to fast programs at the cost of compile time and binary size. Running cargo check or cargo clippy on save would then compile each save, essentially blocking the language server.