The Medallion Architecture is a layered data design pattern — typically Bronze → Silver → Gold — that structures a data lakehouse by progressively refining raw data into trusted, analytics-ready assets. First popularized by Databricks with Delta Lake, the pattern is now format-agnostic and runs on Apache Iceberg, Apache Hudi, and Apache Paimon, making it a universal blueprint for modern data platforms regardless of cloud or vendor. The key mental model is separation of concerns by transformation stage: Bronze preserves raw fidelity, Silver enforces integrity and conformity, and Gold serves specific business consumers — and the boundary between Silver and Gold is best tested by whether a transformation requires domain knowledge (if yes, it belongs in Gold, not Silver).
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Table 1: Core Architecture Layers
Understanding what work belongs in each layer is the foundation of a healthy medallion design. Each layer has a distinct contract: Bronze = truth, Silver = quality, Gold = value. Misplacing logic — especially pushing domain knowledge into Silver — is the single most common failure mode.
| Layer | Example | Description |
|---|---|---|
Raw JSON, CSV, Parquet ingested as-is | • Immutable landing zone for raw data • preserves original fidelity including errors, duplicates, and schema drift • append-only • never transformed | |
Deduplicated, type-cast, null-checked records | • Conformed, validated, integrated data across sources • technical transformations only • no business logic requiring domain knowledge | |
fact_orders, dim_customer, report_revenue_by_region | • Business-ready aggregations modeled for specific use cases • star schema, wide tables, or OBT patterns • optimized for BI and ML |