Why a layered architecture?
Building a data warehouse as one giant stack of tables might look fast in the short term, but it becomes impossible to maintain as the organisation grows. A layered architecture isolates changes in source systems, updates to business rules, and differences in reporting needs from one another, keeping that complexity manageable.
The four core layers
Source Layer: Every system that produces the data — ERP, CRM, e-commerce platform, file-based transfers. This layer is never modified, only read.
Staging Layer: Data arriving from the source is copied into this layer exactly as-is, with no business rules applied yet. The goal is to pull the data once without straining the source system, so every later step can run inside the data warehouse's own environment.
Core / Warehouse Layer: The layer where data is cleaned, deduplicated and structured according to the enterprise data model (typically a dimensional / star schema). This is where Data Governance and Data Quality processes are actually enforced.
Presentation / Mart Layer: High-performance views optimised for a specific department or use case. A separate data mart is built here for finance, another for sales, and so on.
What to watch for between layers
Data quality checks — null rates, referential integrity, unexpected duplicate records — should run automatically at every layer transition. Otherwise a small error at the source can travel unnoticed all the way to the presentation layer and drive the wrong decisions in a management report.
Each layer should also have its own SLA: staging can run daily, the core layer through an overnight batch job, and the presentation layer can update in real time or hourly depending on what the business unit needs. This separation keeps both cost and system load under control.
Conclusion
A layered architecture might look like extra complexity, but it's actually the biggest simplification you can make in the long run: each layer has exactly one responsibility, and a change in one layer doesn't ripple directly into the others. At Vera Teknoloji, we design these four layers into a new data warehouse from day one.