Meta Software Engineer interview questions

Please tell me about a previous project of yours and what you would have to change in order to make it scale to millions of users.

The coding questions are not that hard for both two rounds. In the first round, the two questions are (1) return the sum of the k-largest digits ([0-9]) in the array (2) implement a LRU cache (least recently used) In the second round, the two questions are (1) return the index of the largest element, if more than one element reaches max, pick one unifromly at random; (2) clone a graph. the graph is directed, unweighted and not necessarily fully connected.