Core concepts

The delivery engine turns "I emitted a security event" into "it reliably reached the customer's SIEM" without ever blocking the request, losing an event on a transient outage, or letting one bad destination take down the app.

• Delivery engine — the outbox → pump → sink pipeline and every safeguard on it (batching bounds, retry/backoff, dead-letter, circuit breaker, backpressure).
• Outbox and semantics — what the transactional outbox guarantees, and the honest truth about ordering and duplicates (at-least-once, unordered, dedup by event id).