Cache eviction policies (LRU, LFU, TTL) in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the cache eviction policy that removes the least recently used item.

HLD

if cache.is_full():
    cache.evict_policy = "[1]"

Drag options to blanks, or click blank then click option'

ATTL

BLFU

CLRU

DFIFO

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing LRU with LFU or TTL.

The LRU (Least Recently Used) policy evicts the item that was used the longest time ago.

2fill in blank

medium

Complete the code to set the cache eviction policy that removes the least frequently used item.

HLD

if cache.needs_eviction():
    cache.policy = "[1]"

Drag options to blanks, or click blank then click option'

ARandom

BLRU

CTTL

DLFU

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing LFU with LRU or TTL.

LFU (Least Frequently Used) evicts the item with the lowest access frequency.

3fill in blank

hard

Fix the error in the code to correctly implement a time-based cache eviction policy.

HLD

cache.set_eviction_policy("[1]")
cache.expiry_time = 300  # seconds

Drag options to blanks, or click blank then click option'

ATTL

BLRU

CLFU

DFIFO

Attempts:

3 left

💡 Hint

Common Mistakes

Using LRU or LFU where TTL is needed.

TTL (Time To Live) evicts items after a set time expires.

4fill in blank

hard

Fill both blanks to complete the dictionary comprehension that filters cache entries by TTL and sorts by usage frequency.

HLD

filtered_cache = {k: v for k, v in cache.items() if v.expiry > [1]
sorted_cache = sorted(filtered_cache.items(), key=lambda item: item[1].[2])

Drag options to blanks, or click blank then click option'

Acurrent_time

Blast_used

Cfrequency

Dexpiry

Attempts:

3 left

💡 Hint

Common Mistakes

Using expiry instead of current_time for filtering.

Sorting by last_used instead of frequency.

We filter entries where expiry is greater than current time, then sort by frequency for LFU.

5fill in blank

hard

Fill all three blanks to complete the cache eviction function that uses LRU policy with TTL expiration.

HLD

def evict_cache(cache):
    now = [1]
    valid_items = {k: v for k, v in cache.items() if v.expiry > now}
    lru_key = min(valid_items, key=lambda k: valid_items[k].[2])
    del cache[lru_key]
    return cache

current_time = [3]

Drag options to blanks, or click blank then click option'

Atime.time()

Blast_accessed

Cdatetime.now()

Dexpiry

Attempts:

3 left

💡 Hint

Common Mistakes

Using expiry instead of last_accessed for LRU.

Using datetime.now() inconsistently.

The function uses current time from time.time(), filters valid items by expiry, finds the least recently accessed key, and deletes it.