At $work we write closed source Rust but we do not use Kellnr.

Instead we use a mono-repo, using a workspace, that contains most of our applications and libraries.

Our setup is mostly OK but needs some workarounds for problems we have hit:

• Slow cargo clean && cargo build, to speed this up we use sccache.
• Very slow Docker builds. To speed these up we use cargo chef.
• Slow CI/CD. To speed this up we use AWS instances as Github runners that we shutdown, but do not destroy, after use. This allows us to cache build dependencies for faster builds.

I am generally happy with our setup, but I am a fan of mono-repos. If it ever becomes to difficult to keep compiles times reasonable, I think that we would definitely look at Kellnr.