Data Architecture
Medallion Architecture Explained
Bronze, silver and gold are a useful convention — but only when the responsibilities of each layer are defined precisely.
5 min read
The three layers
Bronze holds data as received, with source fidelity and ingestion metadata preserved. Silver holds cleansed, de-duplicated, conformed data with resolved keys and consistent types. Gold holds business-facing aggregates and data products shaped for consumption.
Why implementations drift
The pattern degrades when teams treat the layer names as folders rather than contracts. Typical symptoms are business logic appearing in bronze, silver tables that differ per consumer, and gold tables that quietly become the integration point between domains.
- Define the grain and key of every silver table
- Forbid business rules before the conformed layer
- Make gold consumption-shaped and disposable — rebuildable from silver
- Apply quality checks at layer boundaries, with recorded outcomes
Medallion is not a data model
Layering describes the flow of data through refinement stages. It does not remove the need for a modelling approach in the conformed layer, whether dimensional, data vault or a domain-oriented model.
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