Comment by hgomersall

Even within what you discuss, things like renderers, audio engines and physics calculations have business logic, which I interpret as being the logic pertinent to their specific tasks, as opposed to support logic. Clearly these sorts of terms are heavily overloaded, so please don't too hung up the precise term I used.

That said, I think the view of systems programming is more relevant. My understanding is essentially the same as Wikipedia: "systems programming aims to produce software and software platforms which provide services to other software, are performance constrained, or both". I don't see business logic excluded from that definition.

For context, the area I use it is in direct interaction with an FPGA in the middle layer of a bigger system. The software acts as a performance critical controller of the FPGA and data marshalling system, controlling the DMAs and shunting the data into the network subsystem. Another bit of the system on different hardware then receives the data and does some performance critical signal processing before passing the result to the application layer. The "systems programming" stuff is responsible for translating high level application API commands into low level FPGA control and low level FPGA data and feedback into high level application structures.

Async works really well on the data handling. I have a full back pressure chain from the application, across the network, across the DMA subsystem right down to the FPGA. It also allows careful pinning of different tasks to different cores with pinned runtimes, which is important in maximising the network throughout on the resource limited cpu cores.

Rust async is great for this kind of stuff. I read a post a while ago, which I annoyingly can't find anymore, in which the author was using custom reactor and executor to hide cache latency. It was really beautiful and incredibly simple and annoyingly forgotten by me (!).