Building AI-Powered API Gateways with YARP and ASP.NET Core

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

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

Complex Request
      |
      v
Large Model

This helps optimize costs and performance.

Multi-Model Routing

Organizations often use multiple models.

Example:

Request
   |
Classifier
   |
 ┌─┴─┐
 |   |
GPT Small
GPT Large

Benefits include:

Cost optimization
Better performance
Improved scalability

The gateway determines which model should process the request.

AI Cost Governance

Gateways provide a centralized location for tracking AI usage.

Monitor:

Token consumption
Request volume
Model usage
Tenant activity

Example:

Daily Tokens

5 Million

Cost governance becomes significantly easier.

Request Transformation

YARP supports request transformation.

Example:

Client Request

Gateway transformation:

Add Tenant Context

Add Correlation ID

Add Metadata

Backend services receive enriched requests.

This improves observability and governance.

Multi-Tenant AI Platforms

Many AI SaaS products support multiple tenants.

Workflow:

Tenant Request
      |
      v
Gateway
      |
      v
Tenant Context
      |
      v
AI Service

The gateway helps enforce tenant isolation.

Integrating AI Agents

AI agents often interact with multiple systems.

Example:

Agent
  |
  v
Gateway
  |
 ┌─┼───┐
 | |   |
CRM ERP Search

The gateway simplifies connectivity.

This reduces agent complexity.

Observability and Monitoring

Gateways provide a natural location for telemetry collection.

Track:

Request latency
Response size
Token usage
Error rates
Authentication failures

Example:

Requests:
100,000

Errors:
0.3%

Centralized monitoring improves operational visibility.

Integrating OpenTelemetry

OpenTelemetry works well with YARP.

Workflow:

Request
   |
Gateway
   |
Trace
   |
Observability Platform

This enables distributed tracing across AI services.

Securing AI Services

Many AI platforms expose sensitive capabilities.

Examples:

Internal knowledge bases
Financial data
Customer records
Enterprise systems

Gateway protections include:

Authentication

Validate identities.

Authorization

Control permissions.

Rate Limiting

Prevent abuse.

Request Validation

Filter malicious input.

Logging

Maintain audit trails.

These protections reduce risk significantly.

Building an AI Operations Dashboard

Gateway telemetry can power dashboards.

Common metrics:

Active users
AI requests
Cost per tenant
Token usage
Model utilization

Example:

Requests:
250,000

Tokens:
75 Million

Latency:
1.2 Seconds

This improves operational awareness.

Real-World Use Cases

AI gateways support many scenarios.

Enterprise AI Platforms

Centralize access to AI services.

Multi-Tenant SaaS

Manage tenant-specific traffic.

Agent Platforms

Coordinate agent communications.

RAG Systems

Route retrieval requests.

AI Operations Platforms

Track costs and performance.

These use cases continue to expand rapidly.

Best Practices

Centralize Authentication

Simplify security management.

Implement Rate Limiting

Protect resources and budgets.

Monitor Everything

Collect detailed telemetry.

Route Intelligently

Match requests to appropriate models.

Enforce Tenant Isolation

Protect customer data.

Track AI Costs

Monitor token consumption continuously.

These practices improve scalability and governance.

Common Challenges

Routing Complexity

AI systems often involve many services.

Cost Visibility

Tracking usage across models can be difficult.

Performance Bottlenecks

Poor gateway design can affect latency.

Security Risks

Centralized systems become attractive targets.

Operational Complexity

Large deployments require careful management.

Proper architecture helps address these challenges.

YARP vs Direct Service Access

Feature	Direct Access	YARP Gateway
Security Management	Distributed	Centralized
Rate Limiting	Per Service	Unified
Observability	Fragmented	Centralized
Multi-Tenant Support	Manual	Easier
AI Cost Tracking	Difficult	Simplified
Request Routing	Static	Flexible

For most enterprise AI platforms, a gateway provides significant advantages.

Conclusion

As AI systems continue to grow in complexity, managing access to models, agents, knowledge services, and microservices becomes increasingly challenging. API gateways provide a centralized solution for handling security, routing, observability, governance, and operational concerns across distributed AI architectures.

YARP offers a powerful and flexible framework for building modern API gateways within the ASP.NET Core ecosystem. By combining intelligent routing, centralized authentication, rate limiting, cost tracking, OpenTelemetry integration, and tenant-aware processing, organizations can create scalable AI platforms that remain secure, observable, and cost-effective.

Whether you're building AI SaaS products, enterprise agent ecosystems, RAG platforms, or cloud-native AI services, an AI-powered API gateway can serve as the foundation for managing and scaling intelligent applications in production environments.