Full-Stack Architecture Patterns

Chapter 8: API Gateway Pattern

8.1 API Gateway Benefits

API Gateway is a single entry point for client requests. It provides routing, authentication, and other cross-cutting concerns.

Key Benefits:

• Single Entry Point: Clients interact with one API
• Request Routing: Routes requests to appropriate services
• Authentication: Centralized authentication and authorization
• Rate Limiting: Control request rates per client
• Load Balancing: Distribute load across service instances
• Request/Response Transformation: Modify requests and responses
• Monitoring: Centralized logging and metrics

Use Cases:

• Microservices architecture
• Multiple backend services
• Need for unified API
• Complex authentication requirements

API Gateway vs Direct Service Access:

• With Gateway: Client → Gateway → Services
• Without Gateway: Client → Services (direct)
• Gateway adds overhead but provides benefits

8.2 Gateway Implementation

Implement API Gateway using dedicated tools or frameworks.

API Gateway Solutions:

• Kong: Open-source API gateway
• AWS API Gateway: Managed service
• NGINX: Reverse proxy and gateway
• Express Gateway: Node.js-based gateway
• Zuul: Netflix gateway (now Spring Cloud Gateway)

// Express Gateway example
const gateway = require('express-gateway');

gateway()
    .load(path.join(__dirname, 'config'))
    .run();

// Route configuration
{
    "pipelines": {
        "default": {
            "apiEndpoints": ["api"],
            "policies": [
                { "rateLimit": { "action": { "max": 100 } } },
                { "proxy": { "action": { "serviceEndpoint": "backend" } } }
            ]
        }
    }
}

Gateway Features:

• Request routing and load balancing
• Authentication and authorization
• Rate limiting and throttling
• Request/response transformation
• Caching
• Logging and monitoring

8.3 Gateway Patterns

Common patterns for API Gateway implementation.

Backend for Frontend (BFF):

• Different gateways for different clients
• Mobile BFF, Web BFF
• Optimized for specific client needs

Gateway Aggregation:

• Combine multiple service calls
• Reduce client round trips
• Improve performance

8.4 Gateway Best Practices

Follow best practices for effective API Gateway usage.

• Keep gateway stateless
• Implement proper error handling
• Use circuit breakers for resilience
• Monitor gateway performance
• Cache responses when appropriate
• Implement proper security