Sleipnir note·2026.03·5 min read
Provenance feels expensive. Until the first time you don't have it.
Two storage invariants get you most of the way.
Every record has a source identifier. Every record has a timestamp. Both are mandatory at write time, not best-effort at read time.
These invariants have one cost (a strict ingestion gateway) and many benefits (every audit, every regulator response, every retroactive investigation).
The first regulator request pays for the rest.
The first time someone asks 'where did this number come from?' and you can answer in twenty minutes, you have already paid back a year of investment in provenance.
The institutions we work with rarely build provenance because it is required. They build it because it makes them faster on the next hard question.