I did this recently, where I compared going through FFI from Java to Rust, vs through gRPC. gRPC wasn't that much slower than FFI, and its benefit would be that

I did this recently, where I compared going through FFI from Java to Rust, vs through gRPC. gRPC wasn't that much slower than FFI, and its benefit would be that I could have 2 services in the network. FFI had overhead, but its performance profile was consistent, very little fluctuation in runtime.