A cache key registered with what regenerates it

A registry of cache keys, maintained by review, one year after the incident that produced it.

return [
    'order:{id}' => [
        'written_by'    => OrderRepository::class,
        'regenerated_by' => 'a database read',
        'if_missing'    => 'a slower request',
    ],
    'report:monthly:{ym}' => [
        'written_by'    => MonthlyReport::class,
        'regenerated_by' => 'a 40-second query',
        'if_missing'    => 'a 40-second request',
    ],
];

The registry has drifted twice in a year and both times the weekly flush test caught it, which is the arrangement working — the registry is documentation and the test is the mechanism. A key added without a registry entry is not detectable by anything, which is the remaining gap and would need a runtime check nobody has written.