Common Redis Use Cases: Caching, Distributed Locks, Counters, Rate Limiting, and More

1. Cache

String type. Example: hot data cache (e.g., reports, popular items), object cache, full-page cache, which can improve access to hot data.

2. Distributed Data Sharing

String type, because Redis is a distributed independent service that can be shared among multiple applications.

Example: distributed session.

<dependency>
  <groupId>org.springframework.session</groupId>
  <artifactId>spring-session-data-redis</artifactId>
</dependency>

3. Distributed Lock

String type using the SETNX command; it succeeds only when the key does not exist, returning true.

public static boolean getLock(String key) {
    Long flag = jedis.setnx(key, "1");
    if (flag == 1) {
        jedis.expire(key, 10);
    }
    return flag == 1;
}

public static void releaseLock(String key) {
    jedis.del(key);
}

4. Global ID

Integer type using INCRBY for atomic increment, e.g., INCRBY userid 1000 to allocate a block of IDs for sharding scenarios.

5. Counter

Integer type using INCR , suitable for page views, likes, etc., with eventual synchronization to a database.

6. Rate Limiting

Integer type using INCR on a key composed of the visitor’s IP and other info; if the count exceeds a threshold, the request is rejected.

7. Bit Statistics

String type with BITCOUNT (bitmap) to store bits efficiently; each character is stored as 8 bits.

set k1 a
setbit k1 6 1
setbit k1 7 0
get k1
/* 6 7 represent modifications of the binary bits of ‘a’ (ASCII 97 = 01100001) */

Examples: online user statistics, retention statistics.

setbit onlineusers 01 
setbit onlineusers 11 
setbit onlineusers 20

Supports bitwise AND, OR, XOR, NOT operations.

BITOP AND destkey key1 key2 ...
BITOP OR destkey key1 key2 ...
BITOP XOR destkey key1 key2 ...
BITOP NOT destkey key

Calculate users online for 7 consecutive days using BITOP AND .

BITOP "AND" "7_days_both_online_users" "day_1_online_users" "day_2_online_users" ... "day_7_online_users"

8. Shopping Cart

String or hash; all operations applicable to strings are also available for hashes.

Key: user ID; field: product ID; value: quantity.

+1: HINCRBY

-1: HDECRBY

Delete: HDEL

All items: HGETALL

Count of items: HLEN

9. User Timeline

Use a Redis list (doubly linked list) as a timeline; insert entries in order.

10. Message Queue

Lists provide blocking pop operations BLPOP and BRPOP with optional timeout, functioning like Java blocking queues.

BLPOP key timeout : removes and returns the first element, blocking until an element is available or timeout.

BRPOP key timeout : removes and returns the last element, similarly blocking.

Queue semantics: FIFO (RPUSH + BLPOP); Stack semantics: LIFO (RPUSH + BRPOP).

11. Lottery

Use Redis set random pop to obtain a random value.

spop myset

12. Likes, Check‑in, Punch‑in

Maintain likes with a set keyed by like:postId .

Like: SADD like:t1001 u3001

Unlike: SREM like:t1001 u3001

Check like: SISMEMBER like:t1001 u3001

All likers: SMEMBERS like:t1001

Like count: SCARD like:t1001

13. Product Tags

Use a set tags:productId to store all tags of a product.

SADD tags:i5001 "画面清晰细腻"

SADD tags:i5001 "真彩清晰显示屏"

SADD tags:i5001 "流程至极"

14. Product Filtering

Use set operations to compute intersections, unions, and differences for multi‑criteria filtering.

// Get difference
sdiff set1 set2
// Get intersection
sinter set1 set2
// Get union
sunion set1 set2

Example: filter iPhone 11 by brand, OS, screen size, and screen type.

sadd brand:apple iPhone11
sadd brand:ios iPhone11
sadd screensize:6.0-6.24 iPhone11
sadd screentype:lcd iPhone11
sinter brand:apple brand:ios screensize:6.0-6.24 screentype:lcd

15. Follow / Recommendation Model

Use sets user:follow and user:fans to represent following and followers.

Mutual follow example:

sadd 1:follow 2
sadd 2:fans 1
sadd 1:fans 2
sadd 2:follow 1

Find users followed by me who also follow them (intersection):

sinter 1:follow 2:fans

Potential acquaintances via set difference:

sdiff 2:follow 1:follow   // for user 1
sdiff 1:follow 2:follow   // for user 2

16. Ranking

Use a sorted set to store click counts.

zincrby hotNews:20190926 1 n6001   // increment news ID 6001

Retrieve top 15 items:

zrevrange hotNews:20190926 0 15 withscores

Redis enables these patterns to build high‑performance backend services.