# Redis Sorted Set ## Overview A Redis sorted set is a collection of unique strings ordered by an associated score. When more than one string has the same score, the strings are ordered lexicographically. Typical use cases: 1. Leaderboard 2. Rate limiter: You can use a sorted set to build a sliding-window rate limiter to prevent excessive API requests. Sorted Sets is a mix between a Set and a Hash. Sorted sets are implemented via a dual-ported data structure contains both a skip list and a hash table, so add operation takes O(logN) time. When we read sorted elements, the operation is O(1). ZRANGE order is low to high, ZREVRANGE order is high to low. ZREVRANK is available to get rank, considering the elements sorted in descending way. {% embed url="" %} ## How to scale Redis cluster? Redis cluster is a cluster architecture of acentric node P2P, and internally it adopts the gossip protocol to transmit and maintain the topological structure of the cluster and the cluster metadata. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://dongzeli95s-organization.gitbook.io/swe-interview-handbook/system-design/deep-dive/redis-sorted-set.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.