When building an event-driven architecture, teams often discuss exactly-once delivery and idempotency as if they were interchangeable concepts. This misunderstanding can lead to unnecessary complexity, increased operational overhead, and, in some cases, unreliable systems. In this talk, I will share a real-world case study from a project where our team fell into this trap. Initially, we assumed that enabling exactly-once semantics in Kafka would solve all our deduplication problems. However, as the system evolved, we realized that this approach didn’t eliminate the need for idempotency at the application level. The result? A complex, hard-to-debug system with redundant safeguards that sometimes worked against each other.

Attendees will learn:

• The key differences between exactly-once delivery and idempotency.
• Why assuming one implies the other can introduce unnecessary complexity.
• How our team untangled this confusion and simplified our architecture.
• Practical guidelines for designing robust, event-driven systems without over-engineering them.

This talk is ideal for engineers and architects working with Kafka and event-driven systems who want to avoid common pitfalls and build more maintainable, scalable architectures.