What is API gateway and when to use it?

Question

Accepted Answer

**API Gateway** — single entry point for all API calls.

**When to use:**
- Microservices architecture.
- Multiple clients (web, mobile, IoT).
- Need centralized authentication.
- Rate limiting and monitoring.

**Responsibilities:**
```
API Gateway:
- Request routing
- Authentication/Authorization
- Rate limiting
- Request/Response transformation
- Load balancing
- Caching
- Logging and monitoring
```

**Examples:**
- Kong, AWS API Gateway.
- NGINX, Zuul.

```
Clients → [API Gateway] → [User Service]
                       → [Order Service]
                       → [Payment Service]
(Single entry point)
```

**Benefits:** Simplified client, centralized security, cross-cutting concerns.

Systems Analyst: What is API gateway and when to use it?