How an LRU cache decides what to throw out

How an LRU cache decides what to throw out

A cache only has so many slots. So what goes when it is full?

Every item you use moves to the front. When a new one arrives and there is no room, the one at the back goes: the one nobody has touched for the longest. That is LRU, least recently used.

Here: A, B, C, D fill four slots. B is used again and jumps to the front. E arrives, and A is out.

Save this for your next system design interview.

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