Apache Kafka is an open source distributed event streaming platform, born at LinkedIn, open-sourced in 2011 and later made an Apache Software Foundation project.
Kafka records message streams in topics split into partitions, stored on disk and replicated across several servers. Order is guaranteed within a partition. Producers and consumers do not know each other: each one reads at its own pace, and a consumer can replay the history.
It is used to move data in real time between systems: change data capture from a database (CDC), event-driven microservice architectures, streaming analytics or ML pipelines. Confluent, founded by Kafka's creators, is its main commercial vendor; AWS (MSK), Aiven and others offer managed services.
Why it matters when hiring
Many resumes list Kafka after plugging a consumer into an existing cluster. Real depth shows in operations: choosing the number of partitions, managing offsets, delivery guarantees (at least once, exactly once), schemas and message evolution. In the interview, ask how the candidate handled consumer lag or a duplicate message.