At-Least-Once: The Default and Its Duplicates

At-least-once is the default in almost every messaging system. Kafka, SQS, Pub/Sub, RabbitMQ all default to at-least-once. The reason: it is the only semantic that guarantees no data loss without the complexity of transactions. The tradeoff is duplicates, which are handled downstream. How Duplicates Happen Downstream Dedup Strategies