CCAAK Questions and Answers

Replication in Kafka ensures that partition data is copied across multiple brokers. This guarantees durability (data survives broker failure) and availability (other replicas can serve as leader if current leader fails).

From Kafka documentation:

“Replication ensures that data is not lost if a broker crashes and that messages remain available even during broker outages.”

B → Correct: Ensures persisted data even after failure.

C → Correct: Allows partition leader failover.

A → Incorrect: Replication may slightly reduce performance.

D → Incorrect: Replication is not a security mechanism.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 6, p. 189–191

Apache Kafka Documentation: Replication Overview

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In Apache Kafka, rack awareness can be used to ensure better fault tolerance and availability by spreading partition replicas across brokers in different racks. The broker configuration property that explicitly indicates the rack a broker belongs to is broker.rack.

As per the official Apache Kafka documentation:

“To assign a broker to a specific rack, configure the broker.rack property in server.properties. This informs Kafka of the rack location for the broker.”

This is useful for features like rack-aware partition assignment and leader election. With broker.rack set, Kafka can make intelligent decisions to ensure that replicas are distributed across racks.

Other options:

client.rack is a client-side setting to inform Kafka of the client’s rack for fetching from the closest replica, not for brokers.

zookeeper.rack and kafka.rack do not exist in Kafka’s official configuration.

Page Reference:

Apache Kafka Documentation, “Rack Awareness” section.

Confluent Kafka: The Definitive Guide, 1st Edition, Chapter 6 (Kafka Cluster), p. 215.

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The linger.ms property defines how long the producer will wait to fill up a batch before sending it. Combined with batch.size, it allows the producer to accumulate more messages, thus improving throughput.

From Kafka documentation:

“If batch.size is not yet reached, linger.ms causes the producer to wait for additional messages before sending the batch.”

A → send.buffer.bytes affects TCP socket size.

B → Correct: Improves batching by adding intentional delay.

C → Reduces bandwidth but not directly batching.

D → A timeout for message delivery, not related to batching.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 5, p. 162

Apache Kafka Documentation: Producer Config – linger.ms

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Apache Kafka's built-in ACL mechanism (SimpleAclAuthorizer) stores ACL data in ZooKeeper. ACLs are propagated to brokers from ZooKeeper and cached in memory for fast lookup.

From Kafka documentation:

“ACLs are stored in ZooKeeper under /kafka-acl and are loaded into each broker at startup and on updates.”

B → Correct: ZooKeeper stores ACLs centrally.

A → Brokers load ACLs but don’t persist them.

C & D → Do not store or manage ACLs.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 9, p. 285

Apache Kafka Documentation: Authorizer Configuration

Kafka's Controller is a broker that also performs controller duties. It is not a dedicated node. Therefore, it continues to host topics, partitions, and leaders just like any other broker.

From Kafka documentation:

“The controller is one of the brokers in the cluster and continues to perform all normal broker functions.”

A → Correct: The controller is also a normal broker with partitions.

B/C/D → Incorrect: Replication and consumer fetches are not tied to the controller.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 6, p. 190

Apache Kafka Documentation: Kafka Controller Behavior

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Kafka uses ZooKeeper as its distributed coordination system. ZooKeeper helps manage cluster metadata and leader election.

A → Correct: Brokers retrieve leader/partition assignments from ZooKeeper.

D → Correct: ZooKeeper is used to elect the controller broker responsible for cluster-wide administrative tasks.

From Kafka documentation:

“ZooKeeper maintains metadata for Kafka, including broker registration and controller election.”

B → Incorrect: Broker scaling is not handled via ZooKeeper.

C → Incorrect: Replication across clusters is not related to ZooKeeper.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 6, p. 189–191

Apache Kafka Documentation: ZooKeeper Integration

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Kafka supports quotas to limit the broker resources each client can use. This is used to prevent one client from monopolizing cluster bandwidth.

From Kafka documentation:

“Quotas can be applied to both producers and consumers. These quotas are enforced based on the number of bytes per second, and they are applied to ensure fair usage of broker resources.”

A. Quotas → Correct: Admins can define quotas on throughput per client ID or user.

B. Consumer Groups → Incorrect: This controls parallelism in consumption but not resource fairness.

C. Rebalancing → Incorrect: This helps with load balancing but not with resource limitation.

D. ACLs → Incorrect: ACLs define access permissions but not resource usage.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 10 (“Administering Kafka”), p. 306–308

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To increase throughput, Kafka recommends allowing larger batches and giving more time for the producer to accumulate records into batches:

batch.size: Increasing this allows more records to be sent in a single request.

linger.ms: Increasing this adds a delay so that the producer can accumulate more messages into a batch.

From Kafka documentation:

“Increasing both batch.size and linger.ms allows the producer to send larger, more efficient batches, improving throughput at the cost of slightly increased latency.”

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 5, p. 162–163

Apache Kafka Documentation: Producer Configuration Parameters

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In Kafka, the Controller is responsible for managing partition leadership. When a broker that was leader for certain partitions goes down, the Controller immediately detects the failure and:

Triggers a new leader election among the in-sync replicas (ISRs) of those partitions.

Updates the partition metadata to reflect the new leaders and notifies the cluster.

Kafka documentation states:

“When a broker fails, the controller triggers a leader election for all partitions previously led by the failed broker.”

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 6, p. 190–191

Apache Kafka Documentation: “Kafka Controller and Leader Election”

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A → Correct: Kafka uses ZooKeeper's ephemeral node (/controller) to elect a single controller. If the node disappears (e.g., due to GC pause or failure), a new controller is elected.“Kafka uses an ephemeral znode in ZooKeeper to hold the identity of the controller.” — Apache Kafka docs

B → Correct: The controller assigns partition leaders after startup or during rebalancing.

C → Correct: The controller epoch is a monotonically increasing number used to detect outdated controller messages.“Kafka uses a controller epoch to avoid split-brain situations. A new controller will increase the epoch.”

Incorrect options:

D → Wrong: Broker ID is not used as epoch.

E → Wrong: Only one active controller at a time, not one per broker.

F → Wrong: Partition assignment to consumers is handled by the consumer coordinator, not the controller.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 6, p. 189–192

Apache Kafka Documentation: “Kafka Controller Design”

When sizing a ksqlDB cluster, the following factors are crucial:

A. Data Schema: Complex schemas may require more CPU/memory for serialization/deserialization.

B. Number of Queries: Each persistent query consumes system resources (CPU, memory).

C. Number of Partitions: Determines parallelism and state store scalability.

From Confluent documentation:

“Cluster capacity planning depends on schema complexity, query concurrency, and partition count.”

D → Incorrect: Encryption impacts producer/broker, not ksqlDB sizing directly.

E → Incorrect: Retention is managed by Kafka, not ksqlDB.

Page Reference:

Kafka: The Definitive Guide, 1st Edition, Chapter 7, p. 225–229

Confluent ksqlDB Documentation: Capacity Planning Guidelines

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