vigilcare-clinical/docs/resilience/climate/2026-06-24-kafka-down-sync-learned.md

Stopping Kafka mid-sync did not block clinical data persistence: the sync batch processor applied the observation to PostgreSQL and left one outbox row pending (processed_at IS NULL). When Kafka restarted, OutboxRelayService drained the backlog within 60 seconds (outbox pending 1 → 0). This demonstrates the intended separation between Tier 1 durable writes and Tier 2 async scoring pipelines — NEWS2 and downstream consumers may lag during broker outages, but observations are not lost and replay correctly once Kafka is available.