Introduction
As organizations adopt Artificial Intelligence across multiple business processes, their application architectures often become increasingly complex. A single AI platform may interact with several Large Language Models (LLMs), vector databases, AI agents, knowledge bases, microservices, and external APIs.
Consider a modern enterprise AI environment:
Customer Support Agent
Document Processing Service
RAG Search Platform
AI Content Generator
AI Workflow Engine
Embedding Service
Analytics Platform
Managing direct communication between clients and all these services quickly becomes difficult.
Questions arise such as:
Which model should handle the request?
How should traffic be routed?
How can authentication be centralized?
How should rate limits be enforced?
How can AI costs be monitored?
How can requests be logged consistently?
This is where an API Gateway becomes essential.
An API Gateway acts as a single entry point for clients while handling routing, authentication, rate limiting, observability, security, and traffic management behind the scenes.
In the .NET ecosystem, YARP (Yet Another Reverse Proxy) provides a powerful framework for building modern API gateways.
In this article, you'll learn how to build AI-powered API gateways using YARP and ASP.NET Core, enabling intelligent routing, centralized governance, and scalable AI architectures.
What Is an API Gateway?
An API Gateway is a centralized component that sits between clients and backend services.
Instead of:
Client
|
+---- Service A
|
+---- Service B
|
+---- Service C
Clients communicate through a gateway.
Client
|
v
API Gateway
|
┌─┼─┐
| | |
A B C
The gateway becomes the central access point.
Why AI Platforms Need API Gateways
AI systems typically involve many services.
Example:
Chat Service
Embedding Service
RAG Service
Agent Service
Analytics Service
Without a gateway:
Client
|
Multiple Connections
With a gateway:
Client
|
Gateway
|
Services
Benefits include:
Simplified architecture
Centralized security
Traffic management
Cost monitoring
Unified observability
These capabilities are critical for enterprise AI systems.
What Is YARP?
YARP stands for:
Yet Another Reverse Proxy
It is an open-source reverse proxy framework built by Microsoft.
YARP provides:
Request routing
Load balancing
Service discovery
Authentication integration
Request transformation
Observability support
Because it is built on ASP.NET Core, it integrates naturally into modern .NET applications.
Understanding Reverse Proxy Routing
A reverse proxy receives incoming requests and forwards them to backend services.
Workflow:
Client
|
v
YARP
|
v
Backend Service
Clients remain unaware of the actual backend implementation.
This improves flexibility and security.
Typical AI Gateway Architecture
A modern AI gateway might look like this:
Client
|
v
YARP Gateway
|
┌─┼────┬────┐
| | | |
LLM RAG Agent Analytics
Each request is routed appropriately.
The gateway becomes the central control layer.
Installing YARP
Create a new ASP.NET Core project.
dotnet new webapi -n AiGateway
Install YARP.
dotnet add package Yarp.ReverseProxy
The application is now ready to act as a gateway.
Configuring YARP
Register YARP in Program.cs.
builder.Services
.AddReverseProxy()
.LoadFromConfig(
builder.Configuration
.GetSection("ReverseProxy"));
This loads gateway configuration from application settings.
Defining Routes
Example configuration:
{
"ReverseProxy": {
"Routes": {
"chatRoute": {
"ClusterId": "chatCluster",
"Match": {
"Path": "/chat/{**catch-all}"
}
}
}
}
}
Requests are routed automatically.
Configuring Clusters
Clusters define backend services.
Example:
{
"Clusters": {
"chatCluster": {
"Destinations": {
"destination1": {
"Address":
"https://chatservice"
}
}
}
}
}
The gateway now knows where to forward requests.
Request Flow
The complete workflow becomes:
Client
|
v
Gateway
|
v
AI Service
|
v
Response
The client interacts with only one endpoint.
Centralizing Authentication
One major advantage of gateways is centralized authentication.
Instead of:
Service A Auth
Service B Auth
Service C Auth
Use:
Gateway Auth
Benefits include:
Simpler management
Consistent policies
Improved security
Authentication can be handled before requests reach backend services.
JWT Authentication Example
Configure authentication:
builder.Services
.AddAuthentication();
Gateway workflow:
Request
|
JWT Validation
|
Authorized Request
Unauthorized traffic can be blocked immediately.
Implementing Rate Limiting
AI services often incur significant costs.
Workflow:
Request
|
Rate Limit Check
|
Allow or Reject
Example:
100 Requests
Per Minute
Rate limiting protects infrastructure and budgets.
AI-Aware Routing
Traditional gateways route requests based on URLs.
AI gateways can route based on request characteristics.
Example:
Simple Request
|
v
Small Model
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