CREATED 2021/11/08 22:16 PM 

Redis

How Redis deletes expired keys

Redis does 10 times per second:

1 Test 20 random keys from the set of keys with an associated expire.

2 Delete all the keys found expired.

3 If more than 25% of keys were expired, start again from step 1.

This is a trivial probabilistic algorithm, basically the assumption is that our sample is representative of the whole key space, and we continue to expire until the percentage of keys that are likely to be expired is under 25%.

https://redis.io/commands/expire#how-redis-expires-keys