Technique prevents duplicate records in financial data pipelines during retries

A data pipeline tutorial demonstrates how to handle retries without creating duplicate records. Financial data systems face particular risks from duplicate ingestion, which can distort totals and create audit issues. The solution involves designing idempotent consumers that process repeated events as if they occurred only once. A Python and SQL pattern uses a composite key of source and source event ID to identify duplicate records. A database uniqueness constraint combined with PostgreSQL's ON CONFLICT clause ensures duplicate events are ignored.