Exactly-once Semantics is Possible: Here's How Apache Kafka Does it

What this post added

This post details the introduction of exactly-once semantics (EOS) in Apache Kafka 0.11 and Confluent Platform 3.3. It explains the challenges of achieving EOS in distributed systems and how Kafka addresses them through two key features: idempotent producers (ensuring messages are written only once per partition, even with retries) and transactions (enabling atomic writes across multiple partitions and committing consumer offsets within the same transaction). The post also explains how these features enable exactly-once stream processing via the Kafka Streams API, guaranteeing that for each received record, its processed results are reflected once, even under failures.