Need a ranking? Pick the structure that keeps members sorted by a number: the score does the sorting.

Choose the type by the shape of the question. A list remembers arrival order, a hash is one record of named fields, and a set only answers is-it-in-there. A sorted set pairs every distinct member with a number and stays arranged by it. For a board that changes constantly and needs the top few at once, let the server do the ordering, not your code.

Read it once, then a question tests whether the trick stuck.