Why use redis

There are mainly the following two aspects

1、 In terms of high concurrency ：

The requests that the direct operation cache can withstand are , Far greater than direct access to the database , So we can consider transferring part of the data in the database to the cache , In this way, some of the user's requests will go directly to the cache without going through the database

2、 In terms of high performance ：

The user accesses some data in the database for the first time , Because it is read from hard profit, this process will be relatively slow , Store the data accessed by the user in the cache , The next time you access this data, you can get it directly from the cache , Operation cache is direct operation memory , So it's pretty fast

Why use Redis Not the others , for example Java Self contained map perhaps guava？

Cache is divided into local cache and distributed cache , image map and guava Local cache , The main characteristics of local cache are lightweight and fast , The life cycle follows jivm The destruction of , In the case of multiple instances , Each instance needs to save a cache , Cache is not consistent

Use redis or memcached It's called distributed caching , In the case of multiple instances , All instances share the same cache as the master The cache is consistent .