Apache Kafka has become the backbone of event-driven architectures at most large companies. Interview questions about Kafka go beyond “what is a topic” — interviewers want to understand how you reason about partitioning strategies, consumer group rebalancing, and the guarantees Kafka actually provides.
These 11 questions cover what senior engineers need to know: how Kafka achieves high throughput, what exactly-once semantics really means, how replication works under the hood, and the operational trade-offs of different configurations. Essential knowledge for anyone building or maintaining event-driven systems.
Kafka's `acks` producer configuration controls how many broker acknowledgements the producer requires before considering a write successful.
Read full answer →Kafka achieves high throughput—millions of messages per second on commodity hardware—through several design decisions that align with how operating systems and hardware actually work, rather than fighting them.
Read full answer →Kafka consumer lag is the difference between the latest offset produced to a partition (log-end offset, LEO) and the last offset committed by the consumer group for that partition.
Read full answer →The In-Sync Replicas (ISR) list is a dynamic set maintained per partition by the Kafka broker acting as partition leader.
Read full answer →A Kafka consumer group is a set of consumers that collaboratively consume messages from one or more topics.
Read full answer →A consumer group rebalance is the process by which Kafka redistributes partition ownership among the members of a consumer group.
Read full answer →`min.insync.replicas` (commonly abbreviated `min.isr`) is a broker/topic-level configuration that specifies the minimum number of replicas that must be in the ISR for a produce request with `acks=all` to be accepted.
Read full answer →`auto.offset.reset` is a consumer configuration that determines where Kafka begins reading messages when a consumer group has no committed offset for a partition — or when the committed offset is out of range (e.g., it was deleted due to log retention).
Read full answer →`enable.auto.commit=true` (the default) instructs the Kafka consumer to automatically commit the current offset to the broker on a fixed interval controlled by `auto.commit.interval.ms` (default 5 seconds).
Read full answer →A Kafka idempotent producer is a producer configured with `enable.idempotence=true` that guarantees exactly-once delivery to a single partition within a single producer session.
Read full answer →A Kafka topic is a named, durable, append-only log that producers write to and consumers read from.
Read full answer →Focus on understanding concepts deeply enough to explain them in your own words. For each topic, practice articulating the trade-offs and real-world applications — interviewers care about practical judgment, not textbook definitions.
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