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Conduktor Gateway data quality Interceptors validate Kafka messages at the proxy layer, before they reach the broker. Rules run per record and have two outcomes: block the record (the producer receives an error) or mark it with a header so consumers can decide what to do. When you mark records, you can also copy the violating records to a dead letter topic.

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When to use data quality interceptors

Use data quality interceptors when you need to:
  • Enforce schema contracts — reject records that don’t match an expected Avro, Protobuf, or JSON Schema
  • Apply business rules — validate field values using CEL expressions (e.g., age > 0, email not null)
  • Prevent bad data propagation — stop invalid records before they reach consumers and cause processing failures
  • Observe without blocking — audit violations in real time without interrupting producer traffic
From our blog: The hidden pitfalls of Kafka’s schemaless data Why schemaless topics let bad data through, and how CEL and JSON Schema rules catch it at the proxy.

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Available policies