Which TWO are true of Event Grid delivery?

1. ✓ A Delivery is at-least-once, so handlers must be idempotent (correct answer)
2. ✓ B Undeliverable events can be preserved by configuring a dead-letter container (correct answer)
3. C Events are delivered in publication order
4. D Exactly-once delivery is guaranteed
5. E Retries continue indefinitely until the handler succeeds

Shortcut: Retries can produce duplicates, so handlers should deduplicate on the event id. Dead-lettering to storage preserves events that exhaust retries. Event Grid makes no ordering promise, and retries are bounded by the event time-to-live, after which the event is dropped unless dead-lettered.