5. Data Quality and Observability Are Non-Negotiable

Data engineers must design systems that are observable — meaning you can detect, trace, and debug issues across the pipeline. The book emphasizes the role of tools like Monte Carlo, Datafold, and Great Expectations for data quality checks, anomaly detection, and validation testing. Just like software engineers use monitoring and logs, DEs must implement alerting for schema drift, null values, or failed loads. The future of data engineering is reliable pipelines. This means test-driven development (TDD) for data, monitoring lineage, and designing feedback loops to ensure trust and traceability.