Response Aggregation — Complete Gateway Composition Guide

In this tutorial, you will learn about Response Aggregation. We cover key concepts, practical examples, and best practices to help you master this topic.

Response aggregation (or response composition) is the ability of an API Gateway to call multiple backend services and combine their responses into a single response for the client.

What You'll Learn

You'll learn when to use response aggregation, implementation strategies, and performance considerations.

Why It Matters

Without aggregation, a client might need 5 API calls to render a single page. Aggregation reduces this to 1 call, improving performance and simplifying client code.

Real-World Use

A product detail page in an e-commerce app needs data from product service, inventory service, pricing service, and review service. The gateway calls all four in parallel and combines responses into one.

Implementation

import aiohttp
import asyncio
from flask import Flask, jsonify

app = Flask(__name__)

SERVICES = {
    "user": "http://user-service:3000",
    "orders": "http://order-service:3001",
    "reviews": "http://review-service:3002"
}

@app.route("/api/dashboard/<user_id>")
async def get_dashboard(user_id):
    async with aiohttp.ClientSession() as session:
        tasks = {
            name: session.get(f"{url}/api/{name}/{user_id}")
            for name, url in SERVICES.items()
        }
        results = await asyncio.gather(*[
            task for task in tasks.values()
        ], return_exceptions=True)
        dashboard = {}
        for (name, _), result in zip(tasks.items(), results):
            if not isinstance(result, Exception):
                dashboard[name] = await result.json()
        return jsonify(dashboard)

Common Mistakes

What's Next

Learn about circuit breaker patterns in API gateways.