What are the key aspects to consider during an ETL code review?

An ETL code review focuses on ensuring that data extraction, transformation, and loading are performed reliably, efficiently, and maintainably. Key aspects include:

1. Data Quality – Verify that null handling, type conversions, and validation rules are correctly applied.
2. Performance – Look for unnecessary scans, suboptimal joins, or repeated computations. Check that batch sizes, indexes, and parallelism settings are appropriate.
3. Modularity & Reuse – Functions should be small, single‑purpose, and testable. Repeated logic should be extracted into helpers.
4. Error Handling & Logging – Ensure that failures are caught, logged with context, and that the pipeline can resume or alert appropriately.
5. Idempotency & Idling – ETL jobs should be safe to rerun without duplicating data. Use upserts or deduplication logic.
6. Security & Compliance – Sensitive data should be masked or encrypted, and access controls should be enforced.
7. Documentation & Tests – Inline comments, README updates, and unit/integration tests help future maintainers.

By systematically evaluating these areas, reviewers can catch bugs early, improve performance, and make the pipeline easier to maintain.