Delivery guarantees
Event brokers typically provide several methods of delivery guarantees. Through the interfaces used to both produce and consume an event (API or SDK), the event broker can ensure how messages are delivered:
- At-most-once delivery
- At-least-once delivery
- Effectively once delivery
The delivery method we choose for any given event depends on which benefit we want to achieve. As we explore each delivery method, we will explore examples that highlight the benefits and trade-offs of each.
At-most-once delivery
At-most-once delivery means that the broker will ensure that a produced event is only delivered at most once (obvious, right?). What this means is as soon as the first consumer processes the event, the broker will not deliver the event to any other consumer. It is at-most-once delivery, so there is a possibility that an event will never be delivered:
- First, the producer does not wait for acknowledgment from the broker that an event...
