Developers who are good with DSA, please share scenarios where you used it to optimise something related to personal/professional projects.

Difficult to explain but I'll try. I had an API which takes a list of complex objects, each object can be a primitive object or refer to one or more other objects in the list, thus a composite object. The processing logic needed the list to be in such a way that if composite object B refers to object A then object A needs to be before B in the list. This orde was not possible to implement on the caller side, meaning caller will pass list in any order. To solve this, I used topological sorting i.e is dependency resolution to sort the list before passing to the processor. I was just a fresher with 6 month of experience under the belt, and this solution helped me draw attention of my teammates and manager to my knowledge and started gaining respect.