In our Invisible City, the subway doesn’t just move people from point A to point B. It moves them through a refinement process.
When data first arrives at the station, it’s usually messy, tired, and covered in “digital mud.” We can’t let them go straight to the Mayor’s office (the Business Dashboard) looking like that! To fix this, Conductor Mickey uses the Medallion Architecture.
It’s a three-stage filtration system that turns “Raw Junk” into “Pure Gold.”
The Medallion Subway: Bronze, Silver, and Gold
The Medallion Architecture is a way of organizing your Delta Tables into three distinct zones. Each zone has a different purpose and a different level of “cleanliness.”
1. The Bronze Station (The Raw Landing)
The Analogy: This is the industrial unloading dock at the edge of the city.
- The Process: We take data exactly as it is from the source—mud, errors, and all. We don’t change a single thing. We just “dump” it into a Delta Table.
- Why? If the “Subway Engine” breaks later, we can always come back here to restart the journey. It’s our ultimate backup.
Mickey’s View: “It’s messy, but it’s honest. This is the raw truth of the city!”
2. The Silver Station (The Cleansing Hub)
The Analogy: This is the city’s massive filtration plant and locker room.
- The Process: Here, Mickey and his team get to work. They:
- Wash the Mud: Remove null values and fix “broken” records.
- Standardize: Ensure all dates and currencies look the same.
- Join: Connect the “Passenger” table with the “Ticket” table so we know who is who.
- The Result: The data is now clean, lean, and ready for work. It’s the “Source of Truth.”
3. The Gold Station (The Executive Suite)
The Analogy: This is the VIP lounge at the Grand Terminal.
- The Process: We don’t just want clean data; we want
- Answers. In the Gold layer, we aggregate the data. We calculate “Total Sales per Hour” or “Top 10 Busy Stations.”
- The Result: The data is stored in small, lightning-fast tables that the “City Mayor” (the CEO) can use to make decisions in seconds.
📐 Technical Blueprint: The Flow of Truth
| Zone | Technical State | Data Quality | Who uses it? |
|---|---|---|---|
| BRONZE | Raw / Ingested | Dirty / Unfiltered | Data Engineers (debugging) |
| SILVER | Cleaned / Augmented | Validated / Joined | Data Scientists & Engineers |
| GOLD | Aggregated / Business | Pure / High-Value | Business Analysts & CEOs |
Why use the Medallion Style?
- Traceability: If a number in a Gold report looks wrong, Mickey can trace it back through Silver all the way to the Bronze “Raw Truth” to find the error.
- Efficiency: Instead of cleaning the data every time someone asks a question, we clean it once (in Silver) and everyone shares the result.
- Safety: It protects the city. If a source system sends “poisoned” data, it gets caught at the Silver filtration plant before it reaches the Gold executive suite.
Conclusion: From Mud to Medals
Building a Data Subway isn’t just about speed; it’s about quality. By using the Medallion Architecture, Mickey ensures that the “Invisible City” isn’t just running—it’s running on pure, refined excellence.