Q:

Unique scoring for redis leaderboard

I am using redis to create a leaderboard and trying to figure out a nice way to deal with players who achieve the same high score (players with the same high score should be ordered by who achieved that high score first)
I had thought of doing the following...
zadd leaderboard highscore.timestamp player_id.attempt_number

However, when I do zrevrange the timestamps are obviously going to be in the incorrect order.
Example input:
zadd leaderboard 20.123 5.1
zadd leaderboard 20.125 5.2
zadd leaderboard 20.012 5.3
zadd leaderboard 21.024 5.4

Output:
zrevrange leaderboard 0 -1
5.4
5.2
5.1
5.3

Desired output:
5.4
5.3
5.1
5.2

A:

One option would be to do zadd leaderboard highscore.(Long.MAX_VALUE - timestamp) player_id.attempt_number (change Long.MAX_VALUE to whatever is a reasonable highest possible value for your timestamp - A signed 64 bit int will store about 300 million years worth of miliseconds, so that might not be needed)
EDIT: Don't forget to add leading zeroes :)

