Kafka Topics & Partitions Flashcards

What is a Kafka 'leader' partition?

Answer: The single replica that handles all reads and writes for a partition

Each partition has exactly one leader replica that handles all producer writes and (by default) consumer reads; followers replicate from it.

What does 'log compaction' do in a Kafka topic?

Answer: Retains only the latest message for each key, removing older duplicates

Log compaction ensures that for each key, only the most recent message value is retained, acting like an upsert store for change-data-capture use cases.

What is the purpose of the `__consumer_offsets` internal topic in Kafka?

Answer: Stores committed consumer group offsets so consumers can resume after restart

__consumer_offsets is an internal Kafka topic that durably stores the committed offsets for all consumer groups.

What is an ISR (In-Sync Replica) set?

Answer: The set of replicas that are fully caught up with the leader's log

The ISR is the subset of a partition's replicas that have replicated all messages up to a configurable threshold and are considered 'caught up' with the leader.

What command lists all topics in a Kafka cluster?

Answer: kafka-topics.sh --bootstrap-server --list

kafka-topics.sh --list with --bootstrap-server connects to the cluster and lists all existing topic names.

What is the impact of increasing the number of partitions on a topic that already has consumers?

Answer: It triggers a consumer group rebalance as partitions are redistributed

Adding partitions to a topic causes the group coordinator to initiate a rebalance so that the new partitions are assigned to consumer group members.