Scalable .NET Internet Banking System Architecture: From Zero to Millions of Users

Introduction

In the era of digital transformation, internet banking has become the backbone of the financial industry. As .NET architects and developers, we bear the immense responsibility of creating systems that are not only secure and reliable but also scalable and high-performing. In this article, we will provide a detailed analysis of how to build a .NET Internet banking system that can scale from zero to millions of users.

System Architecture Evolution:

Let's examine how to plan the evolution of system architecture in line with growing demands.

Initial Stage (0-10,000 users):

At this stage, a simple monolithic architecture is sufficient. We'll use ASP.NET Core Web API, Entity Framework Core, and SQL Server.

Code sample (Startup.cs):

Infrastructure resources:

• 1 x Standard_D2s_v3 Azure VM (2 vCPU, 8 GB RAM)
• 1 x S0 Azure SQL Database (10 DTU, 250 GB storage)

Rationale: At this stage, a simple configuration is sufficient. A single VM provides flexibility and control, while Azure SQL Database offers easy management and automatic backups. JWT authentication ensures secure access to the API, while Swagger facilitates API documentation and testing.

Growth Stage (10,000-100,000 users):

At this stage, we begin horizontal scaling, add caching mechanisms, and improve monitoring.

Code sample (Startup.cs additions):

Infrastructure resources:

• Azure App Service Plan: 2 x P2V2 (2 vCPU, 8 GB RAM each)
• 1 x S1 Azure SQL Database (20 DTU, 250 GB storage)
• 1 x Standard C1 Azure Redis Cache (1 GB, 6,000 connections)
• Azure Front Door
• Application Insights

Rationale:

• App Service provides auto-scaling capabilities.
• Redis Cache reduces database load and accelerates read operations.
• Front Door provides global load balancing and CDN functionality.
• Application Insights gives detailed information about application performance.

Caching service implementation:

Massive Growth Stage (100,000-1,000,000+ users):

At this stage, we transition to a microservices architecture, use different types of databases, and implement asynchronous processing.

Microservice example (AccountService):

Infrastructure resources:

• Azure Kubernetes Service: 3-node cluster (Standard_D4s_v3)
• 1 x P1 Azure SQL Database (125 DTU, 500 GB storage)
• Azure Cosmos DB: 1000 RU/s, Multi-region writes
• Premium P1 Azure Redis Cache (6 GB, 15,000 connections)
• Event Hubs: Standard tier, 20 Throughput Units
• Azure Functions: Premium Plan EP1
• API Management: Standard tier
• Azure AD B2C: P1 tier

Rationale:

• Kubernetes provides high flexibility in managing microservices.
• Cosmos DB ensures global scalability and low latency.
• Event Hubs and Azure Functions help with asynchronous processing, reducing system load during peak hours.
• API Management provides centralized API management and security.
• Azure AD B2C offers a scalable and secure authentication mechanism.

Security and Compliance:

Security is critically important for banking systems. Let's implement the following approaches:

Azure Key Vault for protecting sensitive information:

Always Encrypted in SQL Server for encrypting important data:

SQL Server configuration:

Azure DDoS Protection and Web Application Firewall (WAF):

Azure Portal configuration for DDoS Protection and WAF:

Monitoring and Diagnostics:

Application Insights for telemetry:

Custom metrics:

Performance Optimization:

Asynchronous programming:

Database Optimization:

Resilience and Fault Tolerance:

Circuit Breaker Pattern:

Retry Pattern:

Global Scaling:

Multi-regional deployment using Azure Traffic Manager:

Continuous Integration and Deployment (CI/CD):

Azure DevOps Pipeline for CI/CD:

Conclusion

Building a scalable .NET Internet banking system is a complex task that requires a multifaceted approach. We've examined the evolution of architecture, security considerations, performance optimization, resilience, and global scaling aspects.

It's important to remember that there's no one-size-fits-all solution. Each system has unique requirements and challenges. Continuous monitoring, testing, and optimization are crucial for success.