Data Series: Understanding ETL & Medallion Architecture — Part 1

deepak shankar — Thu, 07 May 2026 07:19:38 +0000

Over the next few posts, I’ll break down understanding analytics pipeline using:
• Databricks
• PySpark
• Delta Lake
• Azure Data Lake Storage (ADLS)

This series is designed for:
✅ Beginners trying to understand ETL practically
✅ Engineers learning Medallion Architecture
✅ Professionals exploring Databricks & Delta Lake
✅ Anyone who wants to understand how real-world data pipelines are built

The goal is simple:
To show how raw, messy datasets become analytics-ready business insights using modern data engineering practices.

Why ETL Matters?
🔍 ETL is NOT just moving data from one place to another.
A production-grade ETL pipeline is responsible for:
• Data ingestion
• Schema handling
• Data validation
• Standardization
• Transformation
• Aggregation
• Data quality enforcement
• Reliable downstream analytics

At first glance, the data can look usable.
But once ingestion started, the real engineering problems appeared.

⚠️ Real-World Data Challenges
Each source can have:
❌ Different schemas
❌ Inconsistent column naming conventions
❌ Missing/null values
❌ Duplicate records
❌ Invalid totals
❌ Mixed data formats
❌ Unstructured entries
❌ Negative or corrupted numeric values

This immediately creates problems for analytics systems. Because if raw data is inconsistent:
→ Dashboards become unreliable
→ Aggregations become inaccurate
→ KPIs lose trustworthiness
This is exactly where ETL pipelines become critical.

To handle this systematically, Medallion Architecture is one of the proven approach

🥉 Bronze Layer
Store raw source data exactly as received.
Purpose:
• Immutable raw storage
• Historical traceability
• Schema preservation
• Reprocessing capability
Technologies:
• ADLS
• Delta Tables

🥈 Silver Layer
Perform cleansing and standardization.
Operations included:
• Null handling
• Schema alignment
• Column normalization
• Deduplication
• Invalid row filtering
• Data type corrections
Goal:
Create trusted, queryable datasets.

🥇 Gold Layer
Build analytics-ready business views.

Why Medallion Architecture Matters?
Instead of building one large transformation script:
✅ Raw data remains untouched
✅ Data lineage becomes traceable
✅ Transformations become modular
✅ Reprocessing becomes easier
✅ Analytics reliability improves
✅ Debugging becomes faster
✅ Pipelines become scalable

A good ETL pipeline is not just about writing Spark code.
It is about:
• Designing resilient data flows
• Handling unreliable source systems
• Maintaining data quality
• Creating scalable analytical foundations
• Enabling trustworthy business insights

In the next post, I’ll break down:
👉 What actually happens inside the Bronze Layer
👉 Why Delta Lake is powerful for raw ingestion
👉 How schema evolution and ACID transactions help in large-scale pipelines

DEV Community: deepak shankar

Data Series: Understanding ETL & Medallion Architecture — Part 1