What is meant by at-least-once delivery?

At-least-once delivery refers to a messaging or data delivery protocol in which each message is guaranteed to be delivered at least one time to the recipient. This ensures that in cases of potential disruptions, such as network failures or processing errors, the system will retry sending the message until it is acknowledged by the recipient.

Focusing on the correct choice, when referencing the concept of at-least-once delivery, it highlights that events or messages are recorded or sent to a destination—such as a data warehouse—at least once, ensuring that no data is lost during transmission. This guarantees data integrity and completeness, which is crucial for analyses and reporting.

In contrast, options that involve messages being delivered multiple times suggest redundancy that may lead to duplicates, not typically the focus of at-least-once delivery. The idea of messages delivered only on request doesn’t align with the proactive nature of at-least-once delivery, where messages are sent without needing specific requests for each one. Lastly, the concept of files being deleted after delivery runs counter to at-least-once principles, which emphasize retaining data until delivery confirmation is received.