Mastering Redis: 16 Real-World Patterns for Caching, Locks, Counters, and More

1. Cache

Use String values for hot data such as report caches, popular items, or full‑page caches to improve read performance.

2. Distributed Data Sharing

Redis, as an independent distributed service, allows String values to be shared across multiple applications, e.g., a distributed session store.

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

3. Distributed Lock

Leverage the SETNX command: it adds a key only when it does not exist, returning true on success.

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

Use an int key with INCRBY for atomic ID generation, e.g., INCRBY userid 1000, useful in sharding scenarios.

5. Counter

Apply the INCR command on integer keys for metrics such as article views or likes; data can be written to Redis first and later synchronized to a database.

6. Rate Limiting

Combine the visitor's IP (or other identifier) as the key and increment a counter; reject requests when the count exceeds a predefined threshold.

7. Bit Statistics

Use String bitmaps with BITCOUNT and related commands. Example:

SET k1 a
SETBIT k1 6 1
SETBIT k1 7 0
GET k1
BITOP AND destkey key1 key2 ...
BITOP OR destkey key1 key2 ...
BITOP XOR destkey key1 key2 ...
BITOP NOT destkey key

Bitmaps are space‑efficient and suitable for large‑scale user‑online statistics.

8. Shopping Cart

Store carts as String or Hash structures. Example key: user ID, field: product ID, value: quantity. Operations include HINCRBY, HDECRBY, HDEL, HGETALL, HLEN.

9. User Timeline

Implement timelines with List (a doubly‑linked list) to maintain ordered entries.

10. Message Queue

Redis List provides blocking pop commands BLPOP and BRPOP with timeout, mirroring Java's blocking queue semantics. RPUSH / BLPOP implements a FIFO queue; RPUSH / BRPOP can also model a LIFO stack.

11. Lottery

Use SPOP to draw a random member from a set.

SPOP myset

12. Likes, Check‑in, Clock‑in

Maintain a set per post, e.g., like:t1001, with commands: SADD like:t1001 u3001 – add a like SREM like:t1001 u3001 – remove a like SISMEMBER like:t1001 u3001 – check existence SMEMBERS like:t1001 – list all likers SCARD like:t1001 – count likes

13. Product Tags

Store tags in a set, e.g., SADD tags:i5001 "clear display".

14. Product Filtering

Combine sets with SDIFF, SINTER, and SUNION to filter products by brand, OS, screen size, etc.

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 for follows ( 1:follow 2) and fans ( 2:fans 1). Intersection finds mutual follows; difference reveals potential acquaintances.

SADD 1:follow 2
SADD 2:fans 1
SINTER 1:follow 2:fans
SDIFF 2:follow 1:follow

16. Ranking

Employ sorted sets for hot‑news ranking:

ZINCRBY hotNews:20190926 1 n6001
ZREVRANGE hotNews:20190926 0 15 WITHSCORES