One must understand what a good underlying implementation looks like to expose a good interface, it's easy to implicitly bake stupid implementations into an int

One must understand what a good underlying implementation looks like to expose a good interface, it's easy to implicitly bake stupid implementations into an interface that cannot be fixed by just changing the implementation. The example that comes to mind is sorting and paging behavior. Junior devs, and many seniors that should know better by now, OFTEN start with requests that use some variant of limit/offset parameters for paging which leads to terrible performance issues and anomalous behavior. How paging works efficiently and what sorting options can be supported with good performance is inherently coupled to the shape of your data and your choice of datastore. People that haven't been through this exercise at a lower layer have little chance of shaping the higher level interface appropriately unless they put work into the implementation up front.