5 / 5 Eviction, TTL & Sizing

Frequency Without Forgetting

Select every statement that is true of a pure LFU cache whose counters only ever increase.

A

Practical implementations add decay, so counters age downward and yesterday's popularity stops pinning entries in place

B

It resists a sequential scan only when every key carries an explicit TTL, because otherwise the scanned keys have no way to leave the cache

C

A key that was extremely hot during a one-time event can occupy space indefinitely, because its counter stays high after the traffic stops

D

A newly inserted key starts near zero and can be evicted almost immediately, even when it is about to become the hottest key

E

It evicts the entry whose last access is oldest, which is why it has to keep every entry in a recency-ordered list rather than a counter per key