I could write a post on things I have learned programming, or I could simply steal this one:https://blog.rpanachi.com/after-25-years-writing-software-here-some-things-learned-so-far

I do wish that US code-based door locks would follow the Korean example and do away with keys. The keyway being the weakest part of the design of the lock.In case the internal battery goes flat the Korean door locks have two exterior terminals which take a 9V battery, which is an elegant solution.