Advanced API Composition

What is API Composition?

API composition allows developers to create a unified interface by merging responses from multiple APIs into a single response. This approach is essential in a microservices architecture to reduce network calls and improve performance.

Benefits of API Composition

• Reduced Latency - Fewer network requests mean faster responses.
• Simplified Client Logic - Clients interact with one endpoint instead of multiple services.
• Decoupled Services - Services can evolve independently without affecting clients.

Common Patterns

• **Backend for Frontend (BFF)**: A layer that serves tailored APIs for different clients.
• **API Gateway**: A single entry point for all client requests that handles routing to various microservices.
• **Orchestrator Pattern**: A service that coordinates multiple backend services to fulfill a single request.

Orchestrator Pattern Example

Below is a simplified example of an orchestrator pattern using Node.js and Express:

const express = require('express');
const axios = require('axios');
const app = express();

app.get('/api/combined', async (req, res) => {
    try {
        const [userData, orderData] = await Promise.all([
            axios.get('http://user-service/api/users'),
            axios.get('http://order-service/api/orders')
        ]);
        res.json({
            user: userData.data,
            orders: orderData.data
        });
    } catch (error) {
        res.status(500).send('Error fetching data');
    }
});

app.listen(3000, () => {
    console.log('Server running on http://localhost:3000');
});
                    

Considerations for Effective API Composition

• **Error Handling**: Implement robust error handling to manage failures in individual services.
• **Caching**: Use caching strategies to minimize repeated calls to backend services.
• **Versioning**: Maintain versioning for your composed API to avoid breaking changes for clients.
• **Security**: Ensure that appropriate security measures are in place, such as authentication and authorization.