Kafka Producers & Consumers Flashcards

What is a 'consumer lag' in Kafka?

Answer: The difference between the latest produced offset and the consumer's current offset

Consumer lag measures how far behind a consumer group is relative to the latest messages produced in a partition.

What does the `fetch.min.bytes` consumer configuration control?

Answer: Minimum data the broker returns in a fetch response before sending

fetch.min.bytes tells the broker to wait until at least that many bytes are available before responding to a fetch request, reducing round trips.

Which of the following accurately describes a 'sticky partitioner' for producers?

Answer: It sends all batched messages to the same partition until the batch is full or linger.ms expires

The sticky partitioner batches records to a single partition until the batch is full or linger.ms fires, then switches, reducing the number of small batches.

When using `assign()` instead of `subscribe()`, what is the consumer responsible for?

Answer: Manually managing partition assignment without group coordinator involvement

assign() gives the consumer direct control over which partitions it reads, bypassing the group coordinator and rebalance protocol entirely.

What type of serializer is required when the producer message key is a String?

Answer: org.apache.kafka.common.serialization.StringSerializer

StringSerializer converts Java String keys/values to bytes, and is the standard serializer when working with string-typed keys.

What is the effect of setting `retries=0` on a Kafka producer?

Answer: The producer will not retry failed sends, potentially losing messages on transient errors

retries=0 disables automatic retry on send failure, meaning any transient network error will result in a lost or failed message.