↓ Background
About Client and Challenges
The legacy system was developed using .NET Framework 4.6.1 and SQL Server. It served as a backend for both Web and Mobile platforms but had significant architectural and maintainability limitations. With the shift toward a new era of .NET Development with MongoDB, the limitations of relying heavily on stored procedures, and the absence of modern practices such as middleware-driven exception handling, structured logging, and modular design became more evident.
With the increasing need for scalability, maintainability, and better developer productivity, a decision was made to migrate the system to .NET 8 with MongoDB as the database engine.
Problems in the Old Project
- Outdated Technology Stack – Limited support for modern libraries and third-party tools.
- No Centralized Error Handling – No middleware, frequent 500 errors without details.
- No Structured Logging – Debugging relied on guesswork.
- Overuse of Stored Procedures – Business logic tied to SQL, reducing flexibility.
- Separate APIs for Web and Mobile – Code duplication, inconsistent behavior.
- Poor Modularity – All components in a single project, hard to scale.
Challenges in the Old Project
- Framework Compatibility Issues – Difficult to adopt modern libraries.
- Database Inconsistencies – Different dev databases for Web/Mobile caused mismatches.
- Operational Risks – Failures hidden by generic errors, no logging.
- Shared Production Database – Staging and production shared same DB, risking stability.
Why Migrate from SQL Server (RDBMS) to MongoDB (NoSQL)?
The shift from SQL Server to MongoDB was not just a database change—it was a paradigm shift in data handling.
Limitations of SQL Server
- Rigid Schema – Adding new fields required migrations and downtime.
- Coupled Business Logic – Heavy stored procedure usage slowed development.
- Scaling Constraints – Vertical scaling was costly, sharding complex.
- Complex Data Models – Nested entities didn’t map well into relational tables.
Advantages of MongoDB
- Schema Flexibility – Documents can evolve without schema migrations.
- Rich Data Structures – Native support for nested objects/arrays, reducing JOINs.
- Horizontal Scalability – Built-in sharding and replication.
- Better API Fit – BSON aligns naturally with REST/GraphQL responses.
Impact on Migration
- Logic Migration – Logic moved from DB to application layer.
- Easier Feature Expansion – Dynamic attributes supported without schema changes.
- Performance Gains – Reduced DB round trips via document embedding.
- Future-Readiness – Enabled analytics pipelines with Change Streams + Elasticsearch.
Migration Objectives
- Upgrade to .NET 8 for performance and long-term support.
- Replace SQL Server with MongoDB for flexibility and scalability.
- Implement centralized exception handling via middleware.
- Introduce structured logging for visibility into API operations.
- Unify Web & Mobile APIs into a single codebase.
- Adopt a modular architecture with separate layers.
- Eliminate stored procedures by shifting business logic to the application layer.
- Enhance Security with JWT/OAuth2.
- Enable CI/CD automation for streamlined deployments.
- Improve Observability with monitoring and tracing.
Proposed New Architecture
Logging
Serilog + MongoDB / Elasticsearch
Database
MongoDB and PostgreSQL
Backend
.NET 8 (Minimal APIs / ASP.NET)
Exception Handling
Custom Middleware
Dependency Injection
Built-in DI in .NET
Performance & Scalability
Swagger/OpenAPI
Key Improvements
- Centralized Middleware with structured error responses.
- Structured Logging with correlation IDs.
- Unified API for both Web and Mobile.
- Modular Project Structure (API, Domain, Infrastructure, Application).
- Enhanced Security with JWT/OAuth2.
- Improved Scalability with cloud-native readiness.
- Automated Testing & CI/CD pipeline integration.
- Better Observability with metrics and tracing.
Expected Outcomes
Improved Maintainability
Clear separation of concerns and reduced code duplication.
Optimized Observability
Full audit trail of API activity for debugging and monitoring.
Scalability & Performance
MongoDB enables faster, schema-flexible data operations.
Future-Aligned Strategy
.NET 8 ensures compatibility with libraries and long-term support.
Conclusion
Migrating from an outdated .NET Framework 4.6.1 + SQL Server setup to a modern .NET 8 + MongoDB architecture addressed the critical pain points of the old system. With schema flexibility, centralized logging, unified APIs, and modular design, the new platform provides scalability, maintainability, and a strong foundation for future growth.