Feature Store · View 09 of 21 · Data
Decisions
- Raw events land immutably before anything is computed from them, so a fixed transformation can re-derive history instead of losing it.
- The contract guard sits between compute and materialisation, not after it: a batch that fails its schema or distribution check is quarantined rather than published, and the last good values keep serving.
- The online store is written from the same computation that writes offline for streaming features, and materialised down from offline for batch ones — freshness where it is needed, provenance where it is affordable.
Assumptions
- 2.6 billion feature values written offline per day; 1.4M events/second into materialisation at peak.
- The stream log retains 7 days, which sets the ceiling on every replay-based recovery.
Risks
- Quarantine protects correctness at the cost of freshness. A source that drifts for a day leaves a group stale for a day, which is the right trade and still a visible outage to the models reading it.