Medallion Architecture is a design pattern that has become the industry standard for Lakehouse environments. It is not a Fabric feature. It describes a way to incrementally improve the quality and structure of data as it moves through three distinct layers: Bronze, Silver, and Gold.
Layer 1: The Bronze Layer (Raw Data)
The Bronze layer is your landing zone. The goal here is data preservation. You bring data in from your source systems (SQL Server, ERP, CRM, IoT logs, or APIs) and store it exactly as it was found.
- Format: Typically stored as files or Delta tables.
- The Rule: No transformations allowed! If the source has a typo or a weird date format, you keep it.
- Why? If you ever need to "replay" your data processing due to a bug in your logic, you have the original source of truth right here in OneLake.
Layer 2: The Silver Layer (Cleansed & Conformed)
This is where the heavy lifting happens. In the Silver layer, you take your raw Bronze data and "clean" it. This is often where Data Engineering personas thrive using Spark Notebooks or Dataflow Gen2.
- Activities: Filtering out nulls, standardizing date formats (YYYY-MM-DD), joining related tables, and deduplicating records.
- The Result: You now have a "Single Source of Truth." If two different source systems have different IDs for the same customer, you resolve that here.
- Storage: Always Delta tables for performance and ACID compliance.
Layer 3: The Gold Layer (Business Ready)
The Gold layer is designed for consumption. This data is curated for specific business departments or use cases (like Sales, Finance, or Marketing).
- Structure: Often organized in a Star Schema (Facts and Dimensions).
- The Goal: Speed and ease of use. A Power BI user should be able to connect to a Gold table and understand exactly what the columns mean without doing any further joining or cleaning.
- Storage: This is often where you might choose between a Gold Lakehouse or a Gold Data Warehouse for final reporting.
Why Medallion Architecture Works Better in Fabric ?
In traditional architectures, moving data between these layers meant complex ETL jobs and moving data between different servers.
In Microsoft Fabric, this process is significantly streamlined:
Zero Data Movement: Because everything is in OneLake, moving from Bronze to Silver is just a matter of a Spark job reading one folder and writing to another.
Shortcuts: You can "shortcut" your Bronze data from an external AWS S3 bucket directly into your Fabric Lakehouse, meaning your "Bronze" layer doesn't even have to physically reside in Azure!
Unified Governance: You can apply security and sensitivity labels across the entire chain, ensuring that raw PII (Personally Identifiable Information) in Bronze is masked by the time it reaches Gold.
Summary of the Medallion Architecture Flow:
