TopolearnSorted sets make leaderboards, priority queues and time-ordered indexes trivial and fast.
A sorted set (zset) is a set where every unique member has a floating-point score, kept in score order (ties broken lexicographically by member). Updates and lookups are O(log N).
ZADD key score memberadds or updates;ZINCRBY key 10 anaadds to a score,ZRANGE key 0 9 REV WITHSCORESgives the top 10 (highest first),ZRANK/ZREVRANKgive a member's position,ZSCOREits score,ZRANGE key 100 200 BYSCOREreturns members with scores in a range; use(for exclusive bounds and-inf/+inffor open ends,ZREM,ZCARD,ZCOUNT key min max, andZREMRANGEBYSCOREto trim.
ZADD flags refine updates: NX only adds new members, XX only updates existing ones, GT/LT only update when the new score is greater/less, perfect for "best score" tables.
Since Redis 6.2, ZRANGE with BYSCORE, BYLEX, REV and LIMIT replaces the older ZRANGEBYSCORE and ZREVRANGE family.
Using timestamps as scores turns a zset into a time index: "events in the last hour" is ZRANGE key (now-3600) +inf BYSCORE, and trimming old entries is ZREMRANGEBYSCORE key -inf cutoff. ZPOPMIN and BZPOPMIN give a priority queue.
Example
redis-cli ZADD game:lb 120 ana 95 ben 150 cy # (integer) 3
redis-cli ZINCRBY game:lb 40 ben # "135"
redis-cli ZRANGE game:lb 0 1 REV WITHSCORES
# 1) "cy" 2) "150" 3) "ben" 4) "135"
redis-cli ZREVRANK game:lb ana # (integer) 2 (0-based)
redis-cli ZADD game:lb GT 100 cy # (integer) 0 lower score ignored
redis-cli ZSCORE game:lb cy # "150"
redis-cli ZRANGE game:lb 100 140 BYSCORE # 1) "ana" 2) "ben"
redis-cli ZCOUNT game:lb '(120' +inf # (integer) 2Remember
- Members are unique and ordered by score; operations are O(log N)
- ZRANGE ... REV WITHSCORES for top-N; ZREVRANK for a member's rank
- BYSCORE with ( for exclusive bounds and -inf/+inf
- Timestamps as scores make a time-ordered index
Watch out for
- Expecting ZRANK to be 1-based: ranks start at 0.