How does redis handle expired elements
Common Expiration Strategies
Scheduled deletion: set a scheduled deletion event for each key value. For example, if a key value expires at 5:00 today, then set an event to execute at 5:00 o’clock and delete its data (advantage: it can be cleared in time by using the memory invalid data
Disadvantage: It will waste a lot of redis resources, because when the amount of data is large, redis is running business, but here is deleting, redis itself is single-threaded, so it will have a great impact on redis performance )
Lazy deletion: When the user accesses the key value, it will verify whether the key value has expired, delete it if it expires, and return directly if it is not expired (advantage: it will not If it is triggered, it will always occupy memory)
Periodic deletion: it is some work to be deleted regularly to ensure that redis can run efficiently and delete invalid information (as shown below)
Redis uses the strategy of lazy deletion + regular deletion to delete
How does redis query a key in massive data
use scan
How does redis query nearby people
How to operate location information in redis: use redis3.2 geo type
The underlying implementation structure: zset ordered collection
The redis version is greater than 3.2 and you need to exclude yourself from the query when querying
