[wyatwerp]

Off-hand, Mirage OS comes to mind - it completely upends how you would "build" and "run" back-end services, and it is written solely in a GC'ed language - OCaml. And all GC'ed languages are not equal; see https://roscidus.com/blog about a Linux package manager ported from Python to OCaml for performance reasons (followed by an OCaml reimplementation of a component in a virtualized OS).

Some infrastructure, e.g. database engines, is ubiquitous, but all instances are of the same few software products written in C/C++/Java. Those ubiquitous instances have banged most bugs out of those codebases, so it is an uphill battle there to convince incumbents and upstarts alike, of the value of a new implementation. But Rust & Pony are marvelously positioned to march up that hill, especially if you throw in multi-threading.

My impression is that only a minority of widely-programmed back-end infrastructure that suits Rust is written in C/C++ (say, map-reduce kernels). The code-base size & the data flow complexity inside those components is pretty limited, and Rust should be tractable at that scale.

Most widely-programmed infrastructure software - in the back-end and on cell phone OS'es - have been merrily using Java/Python/Ruby/Erlang. OCaml is quoted as being used in the management component of VMware. These are much larger applications; is there any evidence or hint that Rust isn't onerous to develop larger systems in? Without that evidence, I feel (not think) that a disciplined GC'ed language (D? Pony?) has a better chance there.