I occasionally watch the Locking Picking Lawyer videos. He has taught me me a few things.
There is no lock that can be opened by a key that can not be picked
The best you can hope for is to have a lock that is very difficult to defeat. A lock picker/thief's biggest enemy is TIME ! The longer it take to open or the louder the process, the more likely the thief will be caught.
Don't have extremely valuable items stored in a place that does not have eyes on it 24/7/365.
Last, good locks ARE EXPENSIVE ! There are no "good" locks available at your "average" store. The best lock cylinders come from Switzerland or Germany.