I haven't done much of what could be called "systems work" in my time with Rust, so it's hard for me to comment on that, but I would tend to assume the overhead

I haven't done much of what could be called "systems work" in my time with Rust, so it's hard for me to comment on that, but I would tend to assume the overhead of these constructs would be extra unappealing in that context, and that instead people would do some combination of re-structuring their code to fit the ownership model and/or using unsafe { }. I guess it also depends on how much memory "churn" your program has. Maybe an operating system keeps objects around for a long time, in which case the overhead of reference-counting diminishes towards negligible. But a web server will typically allocate a bunch of memory and then throw it all away on a per-request basis. If all of this is happening behind ref-counters, I think it will start to become noticeable. Of course, for many kinds of web servers it's very possible to accomplish your goal using single-ownership. But it sounded like that wasn't true in the OP's case.