Building a Scalable API Gateway in .NET with Ocelot

Introduction

In modern software architectures, especially with microservices, managing API traffic efficiently is crucial. An API Gateway acts as the single entry point for client requests, routing them to appropriate backend services while handling authentication, logging, rate limiting, and more. In this article, we explore how to build an API Gateway in .NET using Ocelot, a lightweight and powerful API Gateway library.

Why Use an API Gateway?

API Gateways are essential for:

• Centralized routing: Directs client requests to appropriate services.
• Security & Authentication: Implements JWT-based authentication and authorization.
• Rate Limiting: Prevents abuse by restricting excessive requests.
• Logging & Monitoring: Captures request details for analysis.
• Simplifying Microservices Communication: Provides a unified API for frontend applications.

Setting Up the API Gateway in .NET

1?? Install Dependencies

Create a new .NET Web API project and install Ocelot:

2?? Configure ocelot.json

Define routes to your backend services:

3?? Configure Services in Startup.cs

Modify ConfigureServices() to support authentication and Ocelot:

4?? Configure the Middleware in Startup.cs

Ensure correct middleware order in Configure():

Testing the API Gateway

Run your API Gateway:

Then test your routes:

If everything is set up correctly, the API Gateway will route requests to your backend services.

Deployment to Production

In production, update ocelot.json with real service URLs. Deploy using Azure App Service or Docker:

Conclusion

Building an API Gateway in .NET using Ocelot provides a scalable, secure, and efficient way to manage API traffic. It enables centralized authentication, logging, and service routing. By leveraging JWT authentication and deploying with Docker or Azure, you ensure your system is ready for production.

?? Have you used API Gateways in .NET? Let’s discuss your experience in the comments!