Responsibilities of an API Gateway Authentication, Routing, and Rate Limiting

An API Gateway manages client interactions with microservices, handling security, routing, and load management. In this tutorial, we’ll explore three major responsibilities: Authentication, Routing, and Rate Limiting.

1. Authentication in API Gateway

Authentication ensures that only authorized clients can access backend services.

How Authentication Works

1. Request Handling: The gateway receives a client request.
2. Credential Validation: The gateway verifies the provided credentials (e.g., API keys, JWTs, or OAuth2 tokens).
3. Authorization: If valid, the request is forwarded; if not, an error is returned.

Diagram: Authentication Flow

2. Routing in API Gateway

Routing directs incoming requests to the appropriate microservices.

How Routing Works

1. Receive Request: The gateway receives a client request.
2. Determine Route: It identifies the correct microservice based on the request path, headers, or parameters.
3. Forward Request: The gateway sends the request to the chosen service.

Types of Routing

1. Path-Based Routing
   • Routes based on URL paths, e.g., /api/users goes to the User Service.
2. Header-Based Routing
   • Routes based on headers, useful for differentiating requests from mobile or web clients.
3. Load-Based Routing
   • Distributes requests based on service load to ensure balanced resource use.

3. Rate Limiting in API Gateway

Rate Limiting controls how many requests a client can make within a specified timeframe.

1. Receive Request: The gateway receives a request from the client.
2. Check Request Count: It monitors the client’s request count.
3. Forward or Block: If within limits, the request is forwarded; otherwise, an error is returned.

We have details section on Rate Limiter in our System Design Course.

Advantages of These Responsibilities

1. Centralized Security: Authentication at the gateway ensures consistent security across microservices.
2. Efficient Load Handling: Routing and load-based distribution prevent service overload.
3. Improved Availability: Rate limiting prevents services from being overwhelmed by high traffic.

Conclusion

An API Gateway’s responsibilities of Authentication, Routing, and Rate Limiting ensure secure, efficient, and controlled client communication with backend services. Proper implementation of these tasks optimizes system performance and secures the microservices architecture.