A15. Dead-Letter Queue Investigation Records Records of non-conforming data records caught by ingestion boundary validation. Each record documents what failed, why, and how the issue was resolved. Patterns in dead-letter queue volume reveal upstream data quality trends. The ingestion layer routes records failing schema validation, range checks, or freshness requirements to a dead-letter queue for investigation. Responsible party: Data engineering team investigates and resolves. Technical SME monitors volume trends. Regulations addressed: Article 10(3) (data preparation processes); Article 72 (PMM). Key outputs

• Per-record failure investigation and resolution audit trail
• Volume trend analysis for quarterly PMM review