The DLQ as a Quality Signal

Concepts covered: paDLQAsSignal, paQualitySignal

The intermediate tier introduced the DLQ as durable storage for failed messages. The advanced framing is that the DLQ is also a quality signal. The contents of the DLQ contain information about upstream health, downstream stability, and producer correctness that is not available anywhere else in the system. A growing DLQ is rarely an operational nuisance alone; it is usually a leading indicator of a problem that has not yet manifested in any other dashboard. Reading the DLQ as a signal, not as a queue alone, is the difference between catching an upstream regression on day one and catching it on day fourteen when a consumer notices. Lesson 7 (data quality) treats DLQ growth rate as the most operationally honest data-quality metric. A growing DLQ is a leading indicator of upstream contract d

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