set max-memory inside the config, it'll automatically do it for you as long as you are using expire on the keys. The implementation according to antirez is tha

set max-memory inside the config, it'll automatically do it for you as long as you are using expire on the keys. The implementation according to antirez is that they sample 3 random keys, and expire the soonest one, so put your high priority data with a longer expire and you'll be fine.