Top Kafka Interview Questions and Answers You Should Prepare

To ace your interview, you must prepare the most anticipated Kafka interview questions and answers. The demand for software engineers with certified Apache Kafka expertise is increasing at an exponential rate. Over 60% of the Fortune 100 companies use Kafka, including Goldman Sachs, Cisco, Intuit, Target, and others. The increased popularity of Kafka has resulted in a plethora of job opportunities as well as stiff competition in technical interviews.

Kafka has emerged as a highly attractive option for data integration. It ranks among the top open-source tools for building real-time streaming data pipelines and applications that adapt to the data streams. This article covers the crucial topics that will help you ace your Kafka technical interview rounds.

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Here's what we'll cover:

• Most Popular Kafka Interview Questions and Answers 
• Advanced Kafka Interview Questions and Answers
• Kafka Interview Questions for Practice
• FAQs on Kafka Interview Questions 

Most Popular Kafka Interview Questions and Answers 

You must be thoroughly familiar with the most common topics for Kafka interview questions. Here are some sample Kafka interview questions and answers to help you quickly revise the most vital concepts.

Q1. What is Apache Kafka and why is it used?

Apache Kafka is an open-source, partitioned, and replicated log service and publish-subscribe messaging application. It is also a full-fledged event streaming platform developed by Apache and written in Scala. It is used for building real-time data pipelines and streaming applications.

Q2. What are the main features of Kafka?

You should be well-prepared for Kafka features interview questions. The interviewer can also ask about any one of the features in particular. The top features of Apache Kafka are as follows:

• Kafka is written in the Scala programming language and developed by Apache.
• It is a publish-subscribe messaging system with high throughput and fault tolerance.
• It is deployable in minutes. 
• Kafka is fast because a single Kafka broker can handle megabytes of reads and writes per second and serve thousands of clients.
• You can partition data and streamline over a cluster of machines to enable larger data.
• Confluent Cloud is the cloud Kafka service that provides enterprise-grade features, security, and zero ops burden.
• It offers enterprise-grade security. 
• You can reduce the ops burden using Kafka.
• Kafka has a built-in partition system as a Topic.
• It offers a replication feature.
• A Kafka queue can handle large amounts of data and transfer messages from one sender to another.
• It can also save the messages to storage and replicate them across the cluster.
• It collaborates with Zookeeper to synchronize with other services.

Q3. What are the different components of Apache Kafka?

This is one of the most important Kafka interview questions as the interviewer can ask you to elaborate on the various components too. The important components available in Kafka are as follows:

• Topic: It is a collection or a stream of messages belonging to the same type.
• Producer: It is used to issue communications and publish messages to a specific Kafka topic. It optimizes writing to Kafka.
• Consumer: You can use Kafka consumers to subscribe to a topic and read and process messages from the topic. A consumer facilitates optimal consumption of Kafka data. Their primary role is to take Kafka connection and consumer properties to read the appropriate Kafka broker records.
• Brokers: They are a set of servers capable of storing publisher messages. They manage the storage of messages on the topic.

Q4. What is the significance of ZooKeeper in Kafka? Can we use Kafka without ZooKeeper? 

The ZooKeeper stores offset-related information used to consume a specific topic and by a specific consumer group in the Kafka environment. It builds coordination between different nodes in a cluster. You can also use ZooKeeper to recover from previously committed offset if any node fails because it works as a periodically-commit offset.

It is impossible to avoid Zookeeper and directly connect to the Kafka server. You cannot serve any client request in Kafka if ZooKeeper is down.

Q5. What API architectures does Kafka use?

Kafka uses the following four core APIs:

• Producer API enables an application to publish a stream of records to Kafka topics.
• Consumer API enables an application to subscribe to one or more Kafka topics in addition to allowing the application to process streams of records generated about such topics.
• Streams API allows an application to use a stream processing architecture and process data. You can also use it to take input streams from topics, process them using stream operations, and generate output streams transmitting to more topics. Streams API also helps convert input streams into output streams.
• Connect API or Connector API connects Kafka topics to applications. It constructs and manages the operations of consumers and producers to establish reusable links between these solutions.

Q6. What are the limitations of Kafka?

You should be well-versed with the drawbacks while answering Kafka interview questions. You can consider the following list of disadvantages of Kafka:

• The performance of Kafka degrades when the messages are continuously updated or changed.
• Its throughput gets reduced by brokers and consumers when they have to deal with the data by compressing and decompressing the messages.
• Kafka does not support wildcard topic selection, certain message paradigms such as to request/reply, and point-to-point queues. 
• It lacks a complete set of monitoring tools.

Q7. What is load balancing? How is the load balancing of the server in Kafka done?

Kafka producers handle the load balancing process by default, wherein they spread out the message load between partitions, preserving message ordering. You can specify the exact partition for a message in Kafka. 

Leaders in Kafka perform all read and write requests for the partition, and followers passively replicate the leader. If the leader fails, one of the followers takes over the role, and this entire process ensures load balancing of the servers.

Q8. What roles do Replicas and the ISR play?

Replicas are a list of nodes. They replicate the log for a particular partition irrespective of whether they play the role of the leader. 

ISR stands for In-Sync Replicas, and it is a set of message replicas synced to the leaders.

Advanced Kafka Interview Questions and Answers

You should also prepare some Kafka tough interview questions to nail the most challenging software engineer tech interview rounds at FAANG.

Interviewers often put up Kafka interview questions that require comparisons between Kafka and its alternatives. The following table states the main points of difference between Kafka and RabbitMQ:

Q2. What is the difference between Kafka and Flume?

The major differences between Kafka and Flume are:

Q3. When does QueueFullException occur in Producers?

QueueFullException occurs when the producer tries to send messages at a pace that the broker cannot handle. You will have to add enough brokers to collaboratively handle the increased load as the producer doesn't block.

Q4. What are Znodes in Zookeeper? State the different types of Znodes. 

Znodes are nodes in a ZooKeeper tree. They keep version numbers for data modifications, ACL changes, and timestamps in a structure. ZooKeeper utilizes the version number and timestamp to verify the cache while guaranteeing that updates are well-coordinated. The version number connected grows each time the data on Znode changes. 

There are three types of znodes in ZooKeeper:

• Persistence znodes are the znodes that continue to function even after the client who produced them is disconnected, i.e., they are persistent by default.
• Ephemeral znodes are active only while the client is still alive. These znodes are automatically removed when the client who produced them disconnects. They participate in the election of the leader.
• Sequential znode can be either persistent or ephemeral. The ZooKeeper chooses the sequential number and is pre-fixed when the client assigns a name to the znode.

Q5. What is the Kafka cluster? What happens when the Kafka Cluster goes down?

This is one of the frequently asked Kafka interview questions. A Kafka has one or more brokers that act as the Controller. The producers push records into Kafka topics within the broker while consumers pull records off a Kafka topic.

If one or more brokers of the Kafka cluster are down, the producer will retry for a certain time (based on the settings). One or more of the consumers will not be able to read anything during this time until the respective brokers are up.

Q6. What are the types of system tools?

The three types of system tools are:

• Kafka migration tool that helps to migrate a broker from one version to another.
• Mirror maker assists in offering to mirror one Kafka cluster to another.
• Consumer offset checker shows topic, partitions, and owner for the specified set of topics and consumer group.

Q7. What is a Replication Tool in Kafka? Explain some of the replication tools available in Kafka. 

The Kafka Replication Tool also assists in creating a high-level design for the replica maintenance process. Some replication tools available include:

• Preferred Replica Leader Election Tool
• Topics tool
• Tool to reassign partitions
• StateChangeLogMerger tool 
• Change topic configuration tool

Q8. What are the benefits of using Kafka?

Kafka has the following benefits:

• Scalable: It feeds data over a cluster of machines and partitions to allow large information.
• Quick: Kafka has brokers that can handle thousands of clients
• Durability:  Message is duplicated in the cluster so that there is no record loss.
• Distributed:  Provides fault tolerance and robustness.

Q9. What is BufferExhaustedException in Kafka? What do you understand about the OutOfMemoryException?

A BufferExhaustedException is thrown when the producer is unable to assign memory to a record as the buffer is full. When the production rate exceeds the rate of data transfer from the buffer for long enough, and the producer is in non-blocking mode, the allocated buffer will be depleted, and the exception will be thrown.

An OutOfMemoryException arises when the consumers are sending huge messages, or there is a spike in messages sent at a quicker rate than the rate of downstream processing, and the message queue fills up, consuming memory space.

Q10. Can you change the number of partitions for a topic in Kafka?

Kafka does not permit you to reduce the number of partitions for a topic. However, you can expand the partitions. The alter command enables you to change the behavior and its associated configurations of a topic. You can use the following alter command and increase the partitions to five:

Kafka Interview Questions for Practice

1. What is the main method of message transfer in Kafka?
2. What role does offset play in Kafka?
3. What are leaders and followers in the Kafka environment?
4. What is geo-replication in Kafka?
5. What is log anatomy in Kafka?
6. What is sharding?
7. What is the significance of the retention period in the Kafka cluster?
8. How will you change retention time in Kafka?
9. How is a partitioning key?
10. Explain the following: Kafka Metrics, Log Aggregation, Stream Processing.
11. What is the graceful shutdown in Kafka?
12. What does Kafka guarantee?

This completes the list of Kafka interview questions that you must practice for your next tech interview. The interviewer can ask you to develop a Kafka client application that produces messages to and consumes messages from an Apache Kafka cluster in Java, Kotlin, Python, Ruby, .NET, Scala, or other languages of your choice. 

If you are applying for senior Kafka developer positions, you must practice Kafka coding interview questions to ace the coding rounds. 

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FAQs on Kafka Interview Questions

Q1. How to prepare for Kafka interview questions?

You must compile a list of relevant Kafka projects and accomplishments to discuss while answering Kafka interview questions. To ace your Kafka interview, you must show your enthusiasm for the position. Practice the most common Kafka interview questions, including coding challenges. You can also take a few mock interviews to improve your tech interview preparation.

Q2. What topics should I prepare to ace Kafka interview questions?

You must focus on stream processing, replications, clusters, Kafka features, partitioning, amongst others, to tackle the challenging Kafka interview questions. 

Q3. What questions should I ask the hiring manager in the Kafka interview?

Once the hiring manager is done asking you Kafka interview questions, they will give you some time to ask them questions. You should make the most of this time and ask well-structured questions about your role, the team, and the company. You should not question the basic values or any information you are expected to know beforehand.

Q4. Which companyes use Kafka?

Leading companies worldwide use Kafka to modernize their data strategies with event streaming architecture, including Goldman Sachs, Cisco, Intuit, Netflix, and Airbnb. 

Q5. Can I write Kafka code in Python?

Kafka-python is designed to function much like the official java client, with some pythonic interfaces. You can use Python to write Kafka code as a developer.  

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