Designing Scalable, Resilient and Secure Webhook Processing Architecture on AWS

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Awesome Cloud

5 min readOct 12, 2024

Architecting Serverless (Stripe) Webhook OR Event Notifications Handler on AWS for Scalability, Security, and Fault Tolerance.

Awesome Cloud — Designing Webhook Processing Architecture on AWS

In modern applications, handling webhooks is a critical component, particularly for services like Stripe that rely on them to notify systems about important events such as payment successes, subscription changes, or failed invoices. Designing a scalable, robust, and secure webhook handling architecture is essential to ensure timely processing and to avoid downtime.

In this blog, we’ll design a serverless AWS architecture for handling Stripe webhooks that ensures scalability, high availability, fault tolerance, and security using services like AWS API Gateway, Lambda, EventBridge, DynamoDB, Secrets Manager, and more. This architecture applies to most webhook handling systems.

Architecture

The key to a robust webhook handling system is ensuring that architecture can handle fluctuating traffic, process events securely, and ensure no data is lost due to failures. Here’s a high-level view of how (Stripe) webhooks are handled in our architecture:

Route 53: Configures a custom domain for webhook handling and optionally handles DNS failover.
AWS WAF and Shield: Protects the endpoint from malicious traffic and DDoS attacks. This is optional.
API Gateway: Acts as the entry point for incoming webhook events.
Lambda Authorizer: Validates and authenticates requests before passing them to the backend.
EventBridge: Routes events to specific Lambdas for specialized processing.
Lambda: Processes the webhook event and performs appropriate actions based on type.
DynamoDB: Stores webhook events for persistence, auditing, and replay.
SQS DLQ: Captures failed events for future reprocessing.
SNS: Sends operational alerts for failures and issues.
CloudWatch & X-Ray: Provides monitoring, tracing, and logging.

Let’s break down each component of the architecture in more detail:

Route 53: DNS Management with Failover

Purpose: Route 53 manages DNS for your custom webhook endpoint (e.g., https://webhooks.example.com).

Failover Configuration (optional): You can configure active-passive failover to redirect traffic to another region or backup system in case of failures, ensuring high availability.

AWS WAF: Web Application Firewall

Purpose: Adds an extra layer of security by protecting the API Gateway from malicious traffic, DDoS attacks, or SQL injections.

Configuration:

IP restrictions can be applied to only allow traffic from Stripe’s (or other services) IP addresses.
Implement rate-limiting rules to prevent abusive traffic from overwhelming the system.

API Gateway: Webhook Ingestion and Throttling

Purpose: Serves as the primary entry point for incoming Stripe webhooks. It automatically scales to handle thousands of concurrent requests.

Key Features:

Throttling: Set rate limits to protect downstream services from being overwhelmed.
Request Validation: Ensure incoming requests meet a predefined schema before passing them to Lambda.
Request Transformation: Define how API Gateway transforms [using VTL (Velocity Template Language)] the incoming webhook request (from Stripe or any client) into a format that EventBridge understands. With this there is no need to introduce addtional Lambda function to push events to EventBridge coming from API Gateway.

Lambda Authorizer: Request Authentication

Purpose: A custom Lambda Authorizer authenticates incoming requests, checking for proper headers or tokens.

Stripe Webhook Validation: It verifies the incoming requests against your stored signing secret (retrieved from Secrets Manager) to ensure that only valid requests are processed.

import stripe
import boto3
import os

# Initialize the Secrets Manager client
secrets_client = boto3.client('secretsmanager')

def get_stripe_signing_secret():
    """Retrieve the Stripe signing secret from Secrets Manager."""
    secret_name = os.getenv("STRIPE_SIGNING_SECRET_NAME")  # Set the secret name in environment variable
    response = secrets_client.get_secret_value(SecretId=secret_name)
    return response['SecretString']  # Extract the signing secret

def verify_stripe_signature(event, stripe_signing_secret):
    """Verify the Stripe webhook signature."""
    try:
        # Extract body and headers from API Gateway event
        payload = event['body']
        sig_header = event['headers']['Stripe-Signature']

        # Use the Stripe library to verify the event with the signing secret
        stripe.Webhook.construct_event(payload, sig_header, stripe_signing_secret)
        return True  # Signature valid
    except stripe.error.SignatureVerificationError as e:
        print(f"Signature verification failed: {e}")
        return False  # Signature invalid

def lambda_handler(event, context):
    stripe_signing_secret = get_stripe_signing_secret()

    if verify_stripe_signature(event, stripe_signing_secret):
        # Return 200 OK if signature is valid
        return {
            "statusCode": 200,
            "body": "Authorized"
        }
    else:
        # Return 403 Forbidden if signature is invalid
        return {
            "statusCode": 403,
            "body": "Unauthorized"
        }

AWS Certificate Manager (ACM): SSL/TLS Encryption

Purpose: ACM manages SSL/TLS certificates to ensure secure HTTPS communication between Stripe and your API Gateway.

Security: This ensures end-to-end encryption of webhook payloads and secures sensitive data in transit.

Secrets Manager: Secure Management of Sensitive Data

Purpose: Stores and manages sensitive data like the Stripe Webhook Signing Secret and API Keys.

Benefits:

Encryption at rest.
Automatic rotation of secrets.
Access control via IAM.

EventBridge: Event Routing

Purpose: Routes webhook events based on type. For example, customer.subscription.created might trigger a Lambda that updates customer records, while invoice.paid triggers another workflow.

Benefits:

Decoupled architecture allows for easy integration of new event types.
Rules can filter events and route them to specific services.

Lambda: Webhook Processing

Purpose: Handles the core webhook logic.

Usage:

Event Parsing: Extracts the event data (e.g., payment_intent.succeeded) and process request according to event type, and save data in DynamoDB.
Error Handling: Sends failed events to SQS DLQ for future reprocessing.

DynamoDB: Event Persistence and Auditing

Purpose: Stores all processed webhook events for auditing, reprocessing, and compliance.

Key Features:

TTL (Time to Live): Configures TTL to automatically delete old records after a set period (e.g., 30 days), saving on storage costs.
DynamoDB Streams: Can trigger additional processing for events or analytics.

SQS DLQ: Failure Handling

Purpose: Captures failed webhook events that couldn’t be processed.

Reprocessing: Failed events can be reviewed and manually reprocessed by triggering a Lambda function from the DLQ.

Resiliency and Failure Handling

Resiliency

Multi-AZ Deployment: All services (API Gateway, Lambda, DynamoDB) are deployed across multiple Availability Zones, ensuring the architecture is fault-tolerant.
Route 53 Failover: In the case of a regional failure, DNS failover automatically redirects traffic to another region.

Failure Handling

Automatic Retries: Lambda retries failed executions automatically. If an event cannot be processed after retries, it is sent to the SQS DLQ.

Replay Mechanism

Failed events stored in SQS DLQ can be replayed by manually triggering another Lambda function. This ensures that even failed webhook events can be recovered and processed later.

Security

Stripe Signature Verification: Always validate the webhook signature to ensure that the request is legitimate. Similar mechanism for other services.
TLS Encryption: Enforce HTTPS using ACM to secure communication between Stripe and API Gateway.
IAM Roles: Grant least-privilege permissions to Lambda, EventBridge, and other services to ensure security.
WAF Protection: Leverage AWS WAF to block malicious IPs and prevent DDoS attacks.

Monitoring, Logging, and Alerts

CloudWatch Monitoring

Purpose: Tracks metrics for Lambda invocations, API Gateway requests, DynamoDB performance, and EventBridge routing.

Key Metrics:

Lambda errors and execution times.
API Gateway requests count and latencies.
DynamoDB read/write capacity.

CloudWatch Alarms

Alerts: Set alarms for high error rates, unprocessed events, or sudden increases in DLQ size, triggering notifications via Amazon SNS.

AWS X-Ray

Tracing: Provides distributed tracing, helping you visualize the end-to-end flow of webhook events. This is particularly useful for debugging issues or analyzing performance bottlenecks.

Summary

We can build a robust webhook handling system on AWS (leveraging the right set of services) that is both future-proof and reliable, regardless of volume of events from Stripe or similar services. This architecture ensures your webhook handling is scalable, resilient, cost-efficient, and secure, making it an ideal solution for modern cloud-based applications processing payments and related events.

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