Cache eviction policies (LRU, LFU, TTL) in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does LRU stand for in cache eviction policies?

LRU stands for Least Recently Used. It evicts the cache item that has not been used for the longest time.

beginner

Explain LFU cache eviction policy.

LFU stands for Least Frequently Used. It removes the cache item that has been accessed the fewest times.

beginner

What is TTL in cache eviction and how does it work?

TTL means Time To Live. It sets a fixed time limit for cache items. After this time, the item expires and is removed.

intermediate

Which cache eviction policy is best when recent data is more important?

LRU is best when recent data is more important because it keeps the most recently used items in cache.

intermediate

Why might LFU be less effective in some scenarios compared to LRU?

LFU can keep rarely used but frequently accessed old data, which may waste cache space. LRU adapts better to changing access patterns.

Which cache eviction policy removes the item that was used least recently?

A LRU

B LFU

C TTL

D Random

LRU removes the least recently used item to make space.

What does LFU prioritize when evicting cache items?

A Items with the oldest timestamp

B Items used most recently

C Items used least frequently

D Items with the shortest TTL

LFU evicts items that have been accessed the fewest times.

TTL cache eviction is based on which factor?

A Frequency of access

B Recency of access

C Cache size limit

D Time elapsed since insertion

TTL evicts items after a fixed time since they were added.

Which eviction policy is best for caching session data that expires after a fixed time?

A TTL

B LRU

C LFU

D Random

TTL is ideal for data that should expire after a set duration.

If a cache keeps frequently accessed old data but ignores recent data, which policy might it be using?

A LRU

B LFU

C TTL

D FIFO

LFU can keep old frequently accessed data, ignoring recent usage.

Describe the differences between LRU, LFU, and TTL cache eviction policies.

Think about how each policy decides which item to remove.

Explain when you would choose LRU over LFU or TTL for cache eviction in a system.

Consider what kind of data your system uses most.