Programmer XiaoFu

Jun 23, 2026 · Backend Development

Why Kafka Still Delivers Out‑of‑Order Messages Even When Using the Same Key

Even though Kafka guarantees that messages with the same key land in the same partition, the article explains how producer retries, multithreaded consumer processing, and partition expansion can break ordering, and provides concrete techniques such as idempotent producers and single‑threaded consumption to preserve order.