Free Confluent CCDAK Practice Exam with Questions & Answers | Set: 3

According to the official Apache Kafka Streams documentation, Kafka Streams relies on internal topics (such as changelog topics and repartition topics) to store state, task assignments, and application metadata. These topics are essential for fault tolerance, rebalancing, and state recovery.

When auto-topic creation is disabled, Kafka Streams cannot automatically create the required internal topics unless they already exist. In this situation, the Streams application will fail during startup with a fatal, non-retriable exception, indicating that the necessary internal topics could not be created.

Kafka Streams does not pause or wait for manual topic creation, nor does it operate without storing metadata. Instead, it explicitly requires these topics to exist or be creatable. While administrators can manually pre-create the required internal topics with the correct configuration, failure to do so causes the application to terminate.

Therefore, the correct and documented behavior is that the Kafka Streams application terminates with a non-retriable exception when auto-topic creation is disabled and required internal topics are missing.

To increase consumer throughput, one effective strategy is to increase the amount of data fetched in each poll by raising fetch.max.bytes or max.partition.fetch.bytes. This allows each poll to retrieve more records per request, improving processing efficiency.

From Kafka Consumer Config Docs:

“Increasing fetch size allows consumers to retrieve larger batches of messages, improving throughput and reducing request overhead.”

Removing consumers (A) may reduce parallelism.

Manual commit (C) adds complexity, not throughput.

Decreasing session timeout (D) risks unnecessary rebalances.

Session windows are ideal for tracking periods of activity separated by inactivity, such as user sessions.

From Kafka Streams Documentation > Windowing:

“A session window captures streams of events that are intermittent and separated by a gap of inactivity.”

Tumbling/Hopping/Sliding windows are fixed in size

Session windows are dynamic and close after inactivity timeout

This makes them perfect for identifying gaps in user interaction.

According to the official Apache Kafka consumer semantics documentation, at-most-once delivery means that records may be lost but must never be processed more than once. To achieve this guarantee, a consumer must commit offsets before processing records. If the application crashes after committing but before processing, messages are skipped rather than reprocessed, which satisfies at-most-once semantics.

Option B correctly implements this pattern. It disables automatic offset commits (enable.auto.commit=false) and explicitly calls commitAsync() immediately after polling and before processing records. This ensures that offsets are advanced regardless of whether processing succeeds, eliminating the possibility of duplicate processing.

Option C represents at-least-once semantics, because offsets are committed after processing, which can lead to duplicates on failure. Options A and D rely on automatic commits or incorrect ordering and do not provide strict at-most-once guarantees.

The Kafka documentation explicitly states that manual offset management with commits before processing is required for at-most-once delivery.

Therefore, Option B is the best and officially documented configuration and code skeleton to avoid duplicate message processing.

A: Kafka batches store compression metadata in their headers, indicating how the batch was compressed.

B: Compression is controlled via the producer config compression.type, which defaults to none. Producers explicitly set Gzip or other formats.

From Kafka Producer Docs:

“Compression is done by the producer, and the type is stored in the message batch metadata. The broker does not recompress.”

C is false: messages are serialized before compression.

D is false: messages without keys are distributed across multiple partitions.

For Kafka Streams to perform joins, topics must be co-partitioned, meaning:

They have the same number of partitions (A), and

They use the same partitioning strategy (typically by key) (B)

From Kafka Streams Documentation > Joins:

“Co-partitioning is required for Kafka Streams joins. Topics must have the same number of partitions and use the same key-based partitioner.”

Value schema (C) and retention time (D) have no bearing on join compatibility.

In Kafka Streams, the number of stream tasks = number of input partitions × num.stream.threads × number of instances, but only as many as the number of partitions can actively consume at once.

However, in this case, Kafka Streams assigns one task per partition, and because there are 5 partitions and 15 threads (3 instances × 5 threads), 15 tasks are created, and all 15 can be active depending on processing topology.

From Kafka Streams Developer Guide:

"Kafka Streams creates one task per input partition. If you increase the number of stream threads, it runs multiple tasks in parallel within a single instance."

So, 15 stream tasks will be created and 15 will be actively consuming.