Webhooks & Caching

To move from a "good" API to a "great" API, you need to handle real-time events and optimize for extreme performance.

1. What are Webhooks?

A Webhook is a "Reverse API". Instead of the client polling the server for updates, the server pushes data to the client's URL when an event happens (e.g., a payment succeeded).

// Your API sending a webhook
const payload = { event: 'user.created', data: { id: 123 } };
axios.post(user_webhook_url, payload);

2. Webhook Security

If you are receiving webhooks, you must verify they actually came from the expected source. Use HMAC Signatures in the headers to validate the payload.

3. Server-Side Caching (Redis)

If an endpoint (like GET /products) is called 100 times per second, don't query your database 100 times. Store the result inRedis.

// pseudo-code caching pattern
const cachedData = await redis.get('all-products');
if (cachedData) return res.json(JSON.parse(cachedData));

const products = await Product.find();
await redis.set('all-products', JSON.stringify(products), 'EX', 3600);
res.json(products);

4. Cache Invalidation

The hardest part of caching. When a product is updated, you mustclear or update that key in Redis (redis.del('all-products')) so users don't see stale data.