Eviction and TTL
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
explain how a full cache decides what to drop and how entries expire.
Planned topics
- Eviction applies when memory or size is full: LRU drops the least recently used, LFU the least frequently used.
- LFU protects popular items from one-time scans; LRU adapts faster to changing demand.
- TTL (time to live) removes an entry after a fixed time regardless of use; it bounds staleness.
- Add random jitter to TTLs so entries do not all expire together (see MID-040).
Draft outline details
Demonstration
a 3-slot cache with accesses A B C A D: LRU evicts B; LFU evicts B or C (count 1), keeps A (count 2).
Check your understanding
What does TTL guarantee that eviction does not?
Show answer
An upper bound on how old an entry can be.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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