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Live Event Debugging With ksqlDB at Reddit

Convincing developers to write tests for new code is hard; convincing developers to write tests for new event data is even harder. At Reddit, engineers have often deployed new app versions, only to find out later that the event wasn’t firing at all, or it was missing critical fields. So this begs the question, “How can engineers at Reddit be confident that the events they instrument are accurate and complete?”

In this session, we will learn about an internal tool developed at Reddit to QA events in real-time. This KSQL-powered web app streams events from our pipeline, allowing developers to filter events they care about using criteria like User ID, Device ID or the type of user interaction. With a backbone of KSQL and Kafka Streams, engineers can get real-time feedback on how accurate (or how erroneous) their event data is.


Hannah Hagen

Hannah is a Senior Software Engineer on Reddit’s Data Engineering Team, focusing on streaming pipeline infrastructure and developer tooling. Previously, she worked at Verdigris, where she built the ingestion pipeline for IoT sensor data, ETL jobs, and customer-facing REST APIs.

Paul Kiernan

@Reddit Engineering. Not a cat.