Top Kafka Interview Questions for Freshers and Experienced Developers
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40 Questions
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1
What is a consumer group in Kafka?
easy
consumer-group basics
A consumer group is a set of consumers sharing a group ID. Each partition is consumed by one consumer within the group.
Mention load balancing
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2
How does Kafka rebalance consumers?
medium
rebalance consumer
When consumers join/leave, Kafka redistributes partitions among them. This ensures balanced workload.
Mention impact on latency
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3
What causes frequent rebalancing?
hard
rebalance debugging
Frequent consumer joins/leaves, session timeouts, or slow processing can trigger rebalances.
Mention session timeout
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4
How would you improve Kafka consumer performance?
medium
performance consumer
Increase partitions, optimize batch size, tune fetch settings, and ensure efficient processing logic.
Mention parallelism
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5
What is log compaction?
medium
log-compaction storage
Log compaction retains only the latest record per key, reducing storage while preserving latest state.
Mention use cases
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6
How does Kafka guarantee high availability?
medium
availability replication
Through replication, ISR, and automatic leader election, Kafka ensures minimal downtime.
Mention replication factor
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7
What is the role of acknowledgments in Kafka producer?
medium
producer acks
Acks determine durability guarantees. acks=0,1,all control how many replicas must confirm write.
Compare all values
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8
How does batching improve Kafka performance?
medium
performance batching
Batching groups multiple messages into a single request, reducing network overhead and increasing throughput.
Mention linger.ms
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9
What happens when a Kafka broker goes down?
medium
broker failure
Partitions hosted on that broker become unavailable until a new leader is elected from ISR.
Mention leader election
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10
What is producer retry mechanism?
medium
producer retries
Producer retries sending messages on failure, which may cause duplicates unless idempotence is enabled.
Mention idempotent producer
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11
How would you secure a Kafka cluster?
hard
security authentication
Use SSL/TLS for encryption, SASL for authentication, and ACLs for authorization.
Mention ACLs
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12
What is the difference between Kafka and traditional message queues?
medium
architecture comparison
Kafka is distributed, log-based, and retains messages, while traditional queues delete messages after consumption.
Mention persistence
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13
How does Kafka handle large messages?
hard
performance messages
Kafka allows large messages but recommends external storage and sending references due to performance impact.
Mention max.message.bytes
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14
What is a Kafka topic?
easy
topic basics
A topic is a logical channel where messages are published and consumed, divided into partitions.
Keep definition clear
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15
How does Kafka handle message compression?
medium
compression performance
Kafka supports compression (gzip, snappy, lz4) to reduce network usage and improve throughput.
Mention trade-offs
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16
What is the role of fetch.min.bytes in consumers?
hard
consumer performance
It controls minimum data fetched per request, improving efficiency by reducing small fetches.
Mention batching effect
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17
How does Kafka handle duplicate messages?
medium
duplicates idempotence
Duplicates may occur due to retries. Idempotent producers and transactions help avoid duplicates.
Mention exactly-once
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18
What is transactional messaging in Kafka?
hard
transactions exactly-once
Kafka transactions ensure atomic writes across partitions, enabling exactly-once semantics.
Mention producer config
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19
How does Kafka ensure data consistency?
medium
consistency replication
Through replication, ISR, and controlled leader election, Kafka maintains consistency across replicas.
Mention ISR
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20
What are common causes of Kafka performance degradation?
hard
performance debugging
High disk I/O, insufficient partitions, large messages, and inefficient consumers can degrade performance.
Mention monitoring metrics
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