Apache Kafka Kafka Streams 2

Question 1

What is a 'tumbling window' in Kafka Streams?

Accepted Answer

A fixed-size, non-overlapping time window where each record belongs to exactly one window

Answer

Tumbling windows partition time into equal-sized, non-overlapping buckets so each event falls into exactly one window.

Question 2

What is the purpose of `StreamsConfig.APPLICATION_ID_CONFIG`?

Accepted Answer

Uniquely identifies the Kafka Streams application and is used as the consumer group ID and internal topic prefix

Answer

The application ID serves as the consumer group ID for all internal consumers and is prepended to internal changelog and repartition topic names.

Question 3

What does the `filter()` operation do in a Kafka Streams topology?

Accepted Answer

Passes only records that satisfy a given predicate, dropping the rest

Answer

filter() evaluates a Predicate for each record and only forwards records where the predicate returns true.

Question 4

What is a 'changelog topic' in Kafka Streams?

Accepted Answer

A Kafka topic used to back up local state store contents for fault tolerance

Answer

Kafka Streams writes all state store updates to a changelog topic so that state can be restored from Kafka if a task migrates to another instance.

Question 5

What does `flatMapValues()` do in Kafka Streams?

Accepted Answer

Transforms each record's value into zero or more values, emitting one record per resulting value

Answer

flatMapValues() applies a function to each record's value that returns an iterable, emitting a separate downstream record for each element.

Apache Kafka Practice Test