If Kafka Receives an Event, But the Producer Never Gets the Acknowledgment ? |. FAANG Interview

Kafka Producer ACK Lost? | What Happens Next? | System Design Interview Question for FAANG

Have you ever wondered what happens if Kafka successfully receives an event, but the producer never gets the acknowledgment (ACK)?

This is one of the most frequently asked Kafka System Design Interview Questions for Senior Software Engineers, Staff Engineers, and FAANG interviews.

In this video, we'll walk through a real-world failure scenario that every backend engineer should understand.

You'll learn why duplicate events occur, why retries are unavoidable, and how companies build reliable distributed systems that process business events exactly once—even when networks fail.

📚 In this video you'll learn:

✅ What happens when Kafka receives an event but the producer loses the ACK

✅ Why producer retries are unavoidable

✅ How duplicate Kafka events are created

✅ Why duplicate business processing is more dangerous than duplicate messages

✅ Idempotent Consumer Pattern

✅ Event ID & Deduplication Strategy

✅ Race Conditions in Duplicate Event Processing

✅ Atomic Deduplication using Database Unique Constraints

✅ Consumer Crash Scenarios

✅ Database Transactions for Safe Event Processing

✅ Kafka Idempotent Producer Explained

✅ Kafka Transactions Explained

✅ Transactional Outbox Pattern

✅ Shared Deduplication Store for Scalable Consumers

✅ Event Retention Strategy

✅ Exactly Once Processing vs Exactly Once Delivery

✅ Real-world Kafka System Design Best Practices

🎯 Perfect For
Java Developers
Spring Boot Developers
Backend Engineers
Microservices Developers
Kafka Developers
System Design Interview Preparation
Senior Software Engineer Interviews
Staff Engineer Interviews
Principal Engineer Interviews
FAANG Interview Preparation
🛠 Technologies Covered
Apache Kafka
Java
Spring Boot
Microservices
Distributed Systems
Event-Driven Architecture
Kafka Producer
Kafka Consumer
Idempotency
Event Streaming
Transactional Outbox
System Design
🔥 Interview Questions Answered

✔ What happens if Kafka receives a message but the producer never gets the acknowledgment?

✔ Can Kafka create duplicate events?

✔ Why are retries unavoidable in distributed systems?

✔ How do you prevent duplicate event processing?

✔ What is an Idempotent Consumer?

✔ What is Kafka's Idempotent Producer?

✔ Does Kafka Transaction guarantee Exactly Once Processing?

✔ What is the Transactional Outbox Pattern?

✔ How do large-scale companies handle duplicate events?

What do you think?

How would you design a system to prevent duplicate business processing?

Share your approach in the comments below!

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