In my experience leetcode mostly tests algorithmic thinking. Write a sort function, for example, but the problem is, in real life you use a library with a well

In my experience leetcode mostly tests algorithmic thinking. Write a sort function, for example, but the problem is, in real life you use a library with a well tested, battle-hardened sort implementation. It IS important that you understand the algorithms, but I think they are far less important than data modeling and systems design. In any application, you must be able to understand and design how you model business things, and where you put them, and how and when you access them. Also how you fit a small unit of business logic into the larger picture. This is much harder to test for, since for a given problem there might be multiple, equally valid models and solutions. So obviously the kind of auto-verification leetcode sites do does not work. There must be a human evaluating the solution, which is much more expensive.