Why Does a Data Pipeline Produce Different Results on a Rerun?

A pipeline rerun can produce different output if source data changed, transformations use the current time, records arrive late, or processing is not idempotent. A rerun that silently changes past totals makes audits and customer reports difficult to trust.

What to check

Compare input snapshots, watermark positions, code and configuration versions, timezone assumptions, late-arrival handling, and deduplication keys. Identify whether the pipeline overwrites, appends, or merges results and sample records that changed.

Recommended next step

Make reruns deterministic where practical and record the input and transformation versions used. Define how late data is corrected, and alert when a rerun changes previously published output beyond an expected tolerance.

How Informatix Systems can help

Informatix Systems provides data engineering and analytics services. We can assess the affected setup, trace the issue through relevant systems, and help plan a practical solution. Contact us with the platform involved, when the issue began, and non-sensitive error details.