BigData / Data Lake Interview questions
Explain the Bronze, Silver, and Gold layer architecture in Data Lakes?
The Medallion Architecture is a data design pattern used to logically organize data in data lakes, dividing data into three progressive layers: Bronze, Silver, and Gold. This architecture provides a clear framework for data refinement, quality improvement, and consumption.
| Layer | Purpose | Data Quality | Transformations | Users |
|---|---|---|---|---|
| Bronze (Raw) | Landing zone for raw, unprocessed data from source systems | Unvalidated, may contain duplicates and errors | Minimal or none—preserves original format | Data engineers, data scientists (exploratory) |
| Silver (Refined) | Cleansed, validated, and enriched data | Validated, deduplicated, standardized | Data quality checks, filtering, joins, enrichment | Data engineers, analysts, data scientists |
| Gold (Curated) | Business-level aggregates and analytics-ready datasets | High quality, aggregated, business-ready | Aggregations, denormalization, business logic | Business analysts, BI tools, executives, ML models |
Bronze Layer (Raw Zone): This is the landing zone for all raw, unprocessed data ingested from source systems. Data is stored in its original format with minimal transformation. The bronze layer acts as a historical archive, preserving the complete lineage of data exactly as it was received. Examples include raw JSON files from APIs, CSV exports from databases, streaming event logs, and binary files. This layer is typically append-only, meaning data is never deleted or modified, ensuring complete auditability.
Silver Layer (Refined Zone): Data from bronze undergoes cleansing, validation, and enrichment to create a refined dataset. This layer removes duplicates, corrects errors, standardizes formats, and enforces data quality rules. For example, customer records might be deduplicated, dates standardized to ISO format, and invalid entries filtered out. The silver layer often implements slowly changing dimensions (SCD) and maintains historical snapshots for temporal analysis.
Gold Layer (Curated Zone): This final layer contains business-level aggregates, denormalized tables, and analytics-ready datasets optimized for specific use cases. Gold tables are typically designed for consumption by BI tools, reporting dashboards, and machine learning models. Examples include daily sales summaries, customer 360-degree views, and pre-calculated KPIs. Data is highly curated, performant, and aligned with business requirements.
The medallion architecture promotes data quality by design, enables incremental processing, supports multiple personas, and provides clear data lineage from source to consumption.
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