Where to publish software-related work? I am a researcher in computer science. I am used to publish papers on computer science problem resolution (machine learning, optimization, disabilities, pattern recognition...). 

In recent work, we needed to create a specialized software incorporating many complex technologies. This software is used to conduct other researches on which we already publish. 

We are wondering if we can publish on how the software helps to solve our problem and on how we designed it with multiples technologies. A careful debate on the possibilities, choices and architecture would be incorporated. 
The problem is this is the first time we would publish such article and we don't know where to publish. We are seeking good scientific journals (if possible with an impact factor) accepting such papers. If you know one, can you tell me?
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.