Three log lines that saved an outage

If a config file has more than a dozen options, half of them aren't being used. The other half are being used in ways the original author didn't predict.

I write smaller commits than I used to. The commits are uglier in isolation and much easier to read in sequence.

Caches solve a problem and create three new ones: invalidation, observability, and the slow drift between what the cache thinks is true and what the source thinks is true.