FCMdeliverdPostgresrouterdNATS JetStreamRedisingestdSource systemFCMdeliverdPostgresrouterdNATS JetStreamRedisingestdSource systemalt[first arrival][duplicate]loop[per (individual, channel)]alt[success][transient error][non-retryable]POST /v1/ingest (HMAC-signed, JSON)1Verify HMAC, validate schema2SET dedupe:{key} 1 NX EX 603OK4publish alerts.<company_id> {Alert, dedupe_count=1}5202 Accepted6nil7INCR dedupe:{key} → n8publish alerts.<company_id> {Alert, dedupe_count=n}9202 Accepted (deduped)10deliver Alert11SELECT recipients (batch, prepared)12individuals + channels13publish deliveries.<channel>.<company_id>14deliver job15POST /v1/projects/.../messages:send16200, message_name17UPDATE deliveries SET status='sent'18schedule retry (exp backoff)19publish dlq.<channel>.<company_id>20