Bronze Layer Contract
What the raw landing zone promises and refuses to promise — a faithful replayable copy of the source, with no correction applied.
The value of the raw layer comes from a discipline of restraint: it holds what the source actually sent, unmodified, appended rather than updated, with ingestion metadata attached. It promises replayability. It promises nothing about quality, deduplication, typing or meaning.
That refusal is load-bearing. The moment a "small fix" is applied on the way in — trimming whitespace, coercing a date, dropping an obviously bad row — the layer stops being a faithful record, and the ability to reprocess history through corrected logic is lost, because the corrupted input is gone.
The corresponding rule is that nothing consumes bronze directly except the transformations that produce silver. An analyst querying raw because the cleansed layer was too slow to change is a governance failure with a delivery cause, and it is how two teams end up reporting different revenue: one used the layer that guarantees nothing.