Question 1 of 50
What is Apache Kafka?
Question
"What is Apache Kafka, and how would you describe it to someone who's never heard of it?"
What the interviewer wants to assess
Whether you understand Kafka as a concept — a distributed event log — or just memorized that "it's a messaging tool." It also assesses whether you can explain complex technology clearly, a core skill for senior roles.
Resposta rápida
Kafka is an event streaming platform: a distributed, partitioned, and replicated log where producers publish events and multiple independent consumers read those events at their own pace. Unlike a traditional queue, the event doesn't disappear once read — it stays retained for a configurable period, enabling replay.
Resposta nível Sênior
Kafka solves the coupling problem between a system that produces a business fact and the several systems that need to react to that fact. Instead of the producer calling each consumer directly, it publishes an event to a topic; Kafka stores that event in a distributed log, partitioned across multiple brokers for scale and replicated for fault tolerance. Any number of consumers can read the same event independently, each keeping its own read position. This is fundamentally different from a queue — the message isn't removed once consumed, which enables multiple consumers of the same data and historical reprocessing (replay).
In-depth explanation
See Chapter 1 — What is Apache Kafka? — for the full explanation of the coupling problem that motivated Kafka's creation, the structural difference between an event log and a work queue, and the retention model that enables replay.
Exemplo financeiro
A digital bank publishes the PixRecebido event only once to a Kafka topic. The balance service,
the push notification service, the statement service, and the antifraud service all read that same
event independently — none of them needs to be called directly by the service that received the
PIX.
"Kafka is just another messaging tool"
This answer is too vague and doesn't show understanding of what makes Kafka different. A senior interviewer will push back: "different how?" — and the generic answer doesn't survive the follow-up.
Pode vir a seguir
After this one, expect: "what problem does Kafka solve?", "is Kafka a queue?", and "when would you not use Kafka?".
Related chapters