When to use redis

• There is no need to update in real time, but it consumes a lot of data in the database . For example, the product sales ranking list on the website , This kind of data can be counted once a day , Users don't care if it's real-time .

• Need to be updated in real time , But data that is not updated frequently . For example, a user's order list , He must want to see his orders in real time , But most users don't place orders frequently .

• At a certain time, the data that is accessed heavily and updated frequently . A typical example of this kind of data is the second kill , At the moment of second kill , There may be N Times the usual flow in , The system pressure will be very high . But the cache used for this kind of data cannot be the same as ordinary cache , This cache must be guaranteed not to be lost , Otherwise there will be big problems .