Rule 4 of 8 · Chapter II — Data & Delegation
Collections are caches, not databases.
Why this rule exists
A collection is a point-in-time copy that nothing keeps fresh. Apps that treat collections as the source of truth develop phantom stale-data bugs that vanish on restart — the worst kind to debug.
In practice
Write to the data source and refresh from it; collect only for local performance or offline scenarios, and re-collect after every write that matters.