Semicolony ELI5 · comic

Caching.

Keeping the milk on the counter instead of walking to the fridge every time.

All the way over there?

1
You want milk. It’s in the fridge across the room — the slow, far-away source.
2
First trip is a miss: you walk to the fridge, pay full price, and grab the milk.
3
On the way back you leave it on the counter — a small, fast store close at hand.
Instant. Lovely.

4
Next time is a hit: the milk’s right there, no trip needed.
Wait… is this off?

5
The hard part: a cached copy goes stale the moment the real data changes.
6
So you set a time limit, or toss the copy the instant the source changes — cache invalidation.

Milk on the counter beats walking to the fridge — until the milk goes off. (Bit gets thirsty.)

Semicolony semicolony.dev/eli5/caching/comic