Kafka Interview Questions

Here’s a complete, categorized list of Kafka interview questions — from basic to advanced — that are most commonly asked in backend and system design interviews 👇

---

🧩 1. Basic Level – Core Concepts

These test your fundamental understanding of Kafka.

1. What is Apache Kafka and why is it used?
2. What are Topics, Partitions, and Offsets in Kafka?
3. What is a Producer and a Consumer in Kafka?
4. What is a Kafka Broker?
5. What is a Kafka Cluster?
6. What is a Consumer Group and why is it important?
7. What is a Leader and Follower partition?
8. How does Kafka ensure message ordering?
9. What is the role of ZooKeeper (and what replaced it in new versions)?
10. What is log retention in Kafka and how is it configured?

✅ Tip: Most interviewers start here — make sure you can explain each with a simple example.

---

⚙️ 2. Intermediate Level – Design & Internals

These questions dig deeper into how Kafka works under the hood.

11. How does Kafka achieve high throughput and low latency?
12. What is ISR (In-Sync Replicas) in Kafka?
13. How does Kafka handle message replication and fault tolerance?
14. What happens if a Kafka broker goes down?
15. How does Kafka ensure reliability and durability of messages?
16. What are different types of message delivery semantics in Kafka? (at-most-once, at-least-once, exactly-once)
17. How is offset stored and managed in Kafka?
18. What is the difference between Kafka’s log compaction and log retention?
19. What is the role of partitioning key? What happens if you don’t specify one?
20. How does Kafka handle backpressure when consumers are slow?

✅ Tip: Be ready to explain with diagrams or real-world analogies here.

---

🏗️ 3. Advanced Level – System Design & Real-World Scenarios

These are common in senior-level interviews and system design rounds.

21. How would you design a system using Kafka to process real-time events?
22. How do you achieve exactly-once processing in Kafka?
23. What’s the difference between Kafka and RabbitMQ / other message brokers?
24. How would you scale Kafka consumers to handle increasing load?
25. How do you handle schema evolution in Kafka messages? (Hint: Schema Registry)
26. What are Kafka Streams and how are they different from Kafka Connect?
27. How would you secure a Kafka cluster? (SSL, SASL, ACLs)
28. What are idempotent producers and why are they useful?
29. What is the difference between consumer lag and partition lag? How do you monitor them?
30. How do you handle rebalancing in consumer groups? What problems can it cause?

---

📊 Bonus: Real-World Scenario Questions

These are common in system design-style interviews:

31. Design an event-driven order processing system using Kafka.
32. How would you implement a retry mechanism for failed Kafka message processing?
33. What happens if a consumer crashes after reading a message but before committing the offset?
34. How would you migrate a Kafka topic with zero downtime?
35. How do you guarantee message ordering across multiple partitions?

---

🧠 Pro Tips for Interviews

• 📌 Always mention trade-offs. (e.g., at-most-once vs at-least-once)
• 📈 Use diagrams if it’s a system design question.
• 🔁 Relate Kafka features to real use cases (like order processing, notifications, analytics).
• ⚡ Know key terms deeply: ISR, offset, replication factor, partitioning key, compaction.

---

📚 Quick Revision Table

Concept	Keyword to Remember
Topic	Named stream of data
Partition	Unit of parallelism
Offset	Message position in partition
Producer	Sends messages
Consumer	Reads messages
Consumer Group	Parallel consumption
ISR	Replicas in sync
Delivery semantics	At-most, at-least, exactly-once
Log Compaction	Keeps latest value per key
Schema Registry	Handles schema evolution

---

---

Read other awesome articles in Medium.com or in akcoding’s posts.

OR