Replication factor in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What does the replication factor control in Kafka?

In Kafka, the replication factor is a key configuration. What does it control?

A The number of consumers in a consumer group

B The number of partitions in a topic

C The maximum size of a message in bytes

D The number of copies of each partition across different brokers

💡 Hint

Think about data safety and availability in Kafka.

The replication factor sets how many copies of each partition exist on different brokers. This helps with fault tolerance.

❓ Predict Output

intermediate

Output of creating a topic with replication factor 3

Given the following Kafka topic creation command, what will be the replication factor of the topic?

kafka-topics.sh --create --topic test-topic --partitions 2 --replication-factor 3 --bootstrap-server localhost:9092

A The topic will have 3 copies of each partition on different brokers

B The topic will have 2 copies of each partition

C The topic will have 1 copy of each partition

D The command will fail because replication factor cannot be 3

💡 Hint

Replication factor is set explicitly in the command.

The replication factor option sets the number of copies per partition. Here it is 3, so each partition has 3 copies.

❓ Predict Output

advanced

What happens if replication factor is higher than available brokers?

Consider a Kafka cluster with 2 brokers. What happens if you try to create a topic with replication factor 3?

A The topic creation fails with an error about insufficient brokers

B The topic is created with replication factor 2 automatically

C The topic is created with replication factor 3 but some replicas are on the same broker

D The topic is created with replication factor 1

💡 Hint

Replication factor cannot exceed the number of brokers.

Kafka requires the replication factor to be less than or equal to the number of brokers. Otherwise, topic creation fails.

🧠 Conceptual

advanced

Why is a higher replication factor beneficial?

What is the main benefit of setting a higher replication factor for a Kafka topic?

A Simpler consumer group management

B Reduced disk usage on brokers

C Improved fault tolerance and data availability

D Faster message processing speed

💡 Hint

Think about what happens if a broker fails.

A higher replication factor means more copies of data exist on different brokers, so if one broker fails, data is still available.

🚀 Application

expert

Calculate minimum in-sync replicas for replication factor 5

You have a Kafka topic with replication factor 5. To ensure strong durability, you want to set the minimum in-sync replicas (min.insync.replicas) to the highest number that still allows the leader to acknowledge writes if one broker fails. What should this value be?

A 2

B 4

C 5

D 3

💡 Hint

min.insync.replicas must be less than or equal to replication factor minus one to tolerate one failure.

With replication factor 5, setting min.insync.replicas to 4 means the leader requires 4 replicas to acknowledge writes. This allows one broker to fail and still maintain durability.