I'm in somewhat the same circumstance. Have had a very successful 15 year career until this last iteration of job seeking. In all this time I never bothered learning the grab bag of tricks for mathematically optimizing recursive algorithms because it never came up in the many thousands of lines of codes I've written or code reviewed. I've learned many other hard problems and I can usually run circles around all the super smart new grads with their memorized algorithms, but it doesn't seem to matter now.