Where to publish software-related work?
If the software system is targeted for a research problem that is deep, recognized by the community, requires complex architecture and design, and from which a wide community can benefit from, then system conferences could be a good match. 

I'll give you an example. Symbolic execution is a widely used and researched technique in software verification. People from Stanford developed Klee, a symbolic execution engine that aims to be highly practical and scalable. Making
such a system required taking care of quite some details. They published paper
on OSDI, and I believe they received best paper award. Klee paper. 

Other than that, there might be conferences in your particular area that care
about building systems for the problems you mentioned, but I guess you already took a look into that. Hope this helps.