This behavior is well known in the developer community, since it is the default behavior for the popular memcached system.

Maxmemory configuration directive

The maxmemory configuration directive configures Redis to use a specified amount of memory for the data set. You can set the configuration directive using the redis.conf file, or later using the CONFIG SET command at runtime.

Eviction policies

• noeviction: New values aren’t saved when memory limit is reached.
• allkeys-lru: Keeps most recently used keys; removes least recently used (LRU) keys
• allkeys-lfu: Keeps frequently used keys; removes least frequently used (LFU) keys
• volatile-lru: Removes least recently used keys with the expire field set to true.
• volatile-lfu: Removes least frequently used keys with the expire field set to true.
• allkeys-random: Randomly removes keys to make space for the new data added.
• volatile-random: Randomly removes keys with expire field set to true.
• volatile-ttl: Removes keys with expire field set to true and the shortest remaining time-to-live (TTL) value.

How the eviction process works

• A client runs a new command, resulting in more data added.
• Redis checks the memory usage, and if it is greater than the maxmemory limit , it evicts keys according to the policy.
• A new command is executed, and so forth.