I think the harder part, in my experience, is not just choosing data structures, but choosing ones that will remain relatively flexible through the life of the

I think the harder part, in my experience, is not just choosing data structures, but choosing ones that will remain relatively flexible through the life of the project, and changing them when they become problematic. This is also a difficult investment to justify because, as always, it doesn't deliver any "user facing features". That makes me chuckle because most of the time the "feature" is that it continues to be possible to use the application at all.