Redis Use Cases: Caching, Distributed Locks, Counters, Rate Limiting, Bitmaps, Shopping Cart, Timeline, Queues, and More

1. Caching

String type. Example: hot data caching (e.g., reports, trending topics), object caching, full‑page caching, which can improve access speed for frequently accessed 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.

Example: INCRBY userid 1000 – useful in sharding scenarios to obtain a block of IDs at once.

5. Counter

Integer type, using INCR. Typical uses: article view counts, social media likes, where a slight delay is acceptable (write to Redis first, then sync to DB).

6. Rate Limiting

Integer type, using INCR. Use the visitor's IP (or other identifier) as the key; each request increments the counter, and exceeding the limit returns false.

7. Bitmap Statistics

String type with BITCOUNT (Redis 1.6.6 bitmap data structure). Characters are stored as 8‑bit binary.

set k1 a
setbit k1 6 1
setbit k1 7 0
get k1
/* 6 and 7 represent the 6th and 7th bits of the ASCII code for 'a' (97 → 01100001) */

Typical uses: online‑user statistics, retention tracking.

setbit onlineusers 01
setbit onlineusers 11
setbit onlineusers 20

Supports bitwise AND, OR, XOR, NOT operations.

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

Example: compute users online for seven consecutive days.

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 possible on strings are also available on hashes.

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

Increment: HINCRBY; decrement: HDECRBY; delete: HDEL; get all: HGETALL; count fields: HLEN.

9. User Timeline

Use a LIST (doubly linked list) as a timeline; insertion maintains order.

10. Message Queue

LIST

provides two blocking pop commands: BLPOP and BRPOP, each allowing a timeout. 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, with the same blocking behavior.

These correspond to Java's blocking queue semantics (FIFO queue: RPUSH + BLPOP; LIFO stack: RPUSH + BRPOP).

11. Lottery

Redis provides a random member operation.

SPOP myset

12. Likes, Check‑ins, Clock‑ins

Assume a post ID t1001 and a user ID u3001.

Maintain likes with a set key like:t1001:

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 key tags:i5001 to store all tags for a product.

SADD tags:i5001 "clear picture"

SADD tags:i5001 "true color display"

SADD tags:i5001 "extremely smooth"

14. Product Filtering

// Get difference set
SDIFF set1 set2
// Get intersection
SINTER set1 set2
// Get union
SUNION set1 set2

Example: an iPhone 11 launch.

SADD brand:apple iPhone11
SADD brand:ios iPhone11
SADD screensize:6.0-6.24 iPhone11
SADD screentype:lcd iPhone11

Filter products that are Apple, iOS, screen size between 6.0‑6.24, and LCD:

SINTER brand:apple brand:ios screensize:6.0-6.24 screentype:lcd

15. User Follow & Recommendation Model

Use FOLLOW and FANS sets.

SADD 1:follow 2

SADD 2:fans 1

SADD 1:fans 2

SADD 2:follow 1

Mutual follow (intersection): SINTER 1:follow 2:fans Potential acquaintances (difference):

SDIFF 2:follow 1:follow   // for user 1
SDIFF 1:follow 2:follow   // for user 2

16. Leaderboard

Increment the click count of news item with ID 6001: ZINCRBY hotNews:20190926 1 n6001 Get the top 15 items for today:

ZREVRANGE hotNews:20190926 0 15 WITHSCORES