How redis avoids cache penetration

Redis uses the following methods to avoid cache penetration: 1. Use bloom filters; 2. Set default values; 3. Use empty objects; 4. Use expiration time. Through these methods, Redis can effectively prevent requests from penetrating directly to the database, thereby reducing database pressure.

How Redis avoids cache penetration

Cache penetration means that when non-existent data is requested, Both the cache and the database miss, causing the request to penetrate directly to the database, putting pressure on the database. Redis provides the following methods to avoid cache penetration:

1. Use Bloom filter

The Bloom filter is a probabilistic data structure used for fast Determine whether the element is in the set. In Redis, you can use Redis HyperLogLog (a Bloom filter implementation) to store all possible data keys. When a key is requested, the bloom filter is checked first. If the key does not exist, a null value is returned directly to avoid querying the database.

2. Set default value

For some scenarios, you can set a default value even if the data does not exist. For example, you can set a default user object if the user does not exist. When requesting a non-existent user, there is a miss in both the cache and the database, but instead of penetrating to the database, the default value is returned.

3. Use empty objects

For non-existent data, you can create and cache an empty object. When non-existent data is requested, there is a miss in both the cache and the database, but instead of penetrating to the database, an empty object is returned.

4. Use the expiration time

to set the expiration time for cached data. When data expires, the cache is automatically cleared. When requesting expired data, the cache will miss and the database will need to be queried. This method can effectively prevent cache penetration, but expired data needs to be cleaned regularly to avoid the cache taking up too much space.

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