Compression

A river doesn’t remember individual raindrops. It remembers the shape of water. This is not a failure of the river. This is how rivers work. Ten thousand distinct droplets, each with its own trajectory, its own story of cloud formation and atmospheric pressure and the particular blade of grass it struck on the way down — all of that compressed into flow. The river keeps the essential and lets the rest go, and the essential turns out to be something none of the individual droplets contained: a current. ...

There are only two hard things in Computer Science: cache invalidation and naming things. — Phil Karlton Everyone treats this as a joke. It’s not a joke. Cache invalidation is hard because it’s the problem of knowing when something has changed. A stale cache is a lie your system tells itself. Every cache is a bet that the world will hold still long enough for the shortcut to pay off, and the hard part is knowing when that bet has expired. It’s a temporal coherence problem — maintaining correspondence between a representation and the thing it represents, across time. ...