I've encountered concurrency challenges in my day-to-day work that have no cookie cutter solutions, are specific to my application (particularly in constraints and requirements), and I haven't even been able to fully convince myself of the correctness of my own solution, let alone contrive a way of systematically proving or even testing it.
On the other hand, programmers faced with solving technical challenges such as optimizing and approximating in the face of limited resource, where heuristics and intuition only discovered and learned through experience and trial-and-error (pattern building and "finding" at its best). These meta "design patterns" aren't found in any books yet, especially because they are pretty hard to articulate using the English language.
There is an inventive element to the sort of problem solving that good programmers perform that goes well beyond pasting solutions from StackOverflow. This is why duct tape and bubble gum cobbling of out-of-the-box solutions rarely works in practice (and why good engineers are paid so well). Clever hacks are actually pretty damn clever.
It's scary how many "best practices" I've only learned through building my own production systems and having actual users test what I've coded -- having already done a fair deal of sitting in classrooms being inundated with CS theory from the very minds who conceived it -- even years of building pet projects of my own haven't prepped me for the challenges I am encountering now.
