Webhooks Explained: How to Build Real-Time Integrations

Webhooks enable real-time communication between applications. Instead of repeatedly checking for updates, you receive instant notifications when events happen.

How Webhooks Work

1. You register a URL (endpoint) with a service
2. When an event occurs, the service sends an HTTP POST request to your URL
3. Your endpoint processes the data and responds

Think of it like a doorbell vs constantly checking the door.

Webhooks vs Polling

| Feature | Webhooks | Polling | |---------|----------|---------| | Speed | Instant | Delayed | | Efficiency | Low resource use | High resource use | | Complexity | Moderate | Simple | | Reliability | Needs retry logic | Self-recovering |

Implementing a Webhook Endpoint

Basic Structure

Your webhook endpoint should:

1. Receive the POST request
2. Verify the signature (security)
3. Respond with 200 immediately
4. Process the data asynchronously

Security

Signature Verification: Most services sign webhook payloads with a secret key. Always verify signatures to prevent spoofing.

HTTPS Only: Never accept webhooks over HTTP. Always use HTTPS with a valid SSL certificate.

IP Whitelisting: If the service provides a list of sending IPs, whitelist them.

Idempotency

Webhooks can be delivered more than once. Design your handler to be idempotent — processing the same webhook twice should produce the same result. Use event IDs to detect duplicates.

Quick Response

Respond with a 200 status code quickly (within 5 seconds). Do heavy processing asynchronously after responding. Services will retry if they don't get a timely response.

Common Webhook Use Cases

Payment Processing

Stripe, PayPal, and other payment providers send webhooks for:

• Payment completed
• Subscription renewed or cancelled
• Refund processed
• Payment failed

E-commerce

• Order placed
• Inventory updated
• Shipping status changed
• Customer account created

CRM and Marketing

• New lead captured
• Contact updated
• Email opened or clicked
• Form submitted

Development

• Code pushed to repository
• CI/CD build completed
• Issue created or updated
• Deploy succeeded or failed

Building Robust Webhook Handlers

Queue Processing

Don't process webhooks inline. Push them to a message queue (Redis, RabbitMQ, SQS) and process asynchronously.

Retry Logic

Implement your own retry logic for outgoing webhooks:

• Attempt 1: Immediately
• Attempt 2: After 5 minutes
• Attempt 3: After 30 minutes
• Attempt 4: After 2 hours
• Attempt 5: After 24 hours

Logging

Log every webhook received with:

• Timestamp
• Source service
• Event type
• Payload (sanitized)
• Processing result

Monitoring

Set up alerts for:

• Failed webhook processing
• Unusual webhook volume
• Missing expected webhooks
• High processing latency

Testing Webhooks

• ngrok: Expose local servers to the internet for testing
• webhook.site: Inspect webhook payloads without writing code
• Postman: Send test webhook payloads manually

Webhooks are the glue of modern integrations. Master them and you can connect any systems in real-time.