Home/ Projects/ Backend/E-Commerce Payment Gateway Webhook Handler

Step-by-step guideIntermediateBackend Estimated: Weekend Est. 6h total

Progress:

E-Commerce Payment Gateway Webhook Handler

Secures payment gateway integrations using HMAC signature verification.

Tech Stack:Node.jsExpressCryptoMongoDB

Roadmap Steps

Key Features

Concepts

Tech Stacks

Common Pitfalls

Prequisites

Interactive Project Checklist

Tick off requirements as you build to track real-time completion.

Completed

Step-by-Step Development Roadmap

Follow this chronological guide to build the project from scratch.

0 / 4 Steps Completed

Step 1

Raw Body Middleware Parser

3 key tasks

Capture unmodified payload body buffers from payment gates.

Key Implementation Tasks

Configure Express to store raw request body as Buffer on req.rawBody
Ensure JSON parser does not touch specific /webhook URL paths to prevent validation mismatch
Log incoming headers and verify webhook format structure

Step 2

HMAC Signature Verification

3 key tasks

Step 3

Idempotency & Database Ledger Updates

3 key tasks

Step 4

Event Broadcasting & Queueing

3 key tasks

Common Challenges & Debugging Solutions

Real issues students hit during development and how to troubleshoot them fast.

State Management

Replay Attack Vulnerabilities

Issue: Hackers intercept valid webhook payloads and re-send them to trigger duplicate purchases or credits.

Fix Solution:Extract timestamp header from signature, verify it is within a 5-minute threshold, and validate hash includes the timestamp.

Database Connection

Out of Order Delivery Race Conditions

Issue: Webhook payment.succeeded fires before user signup API completes, referencing missing customer ID records.

Fix Solution:Implement upsert logic or temporary holding collections when reference IDs do not exist, retrying association periodically.

API Errors

Signature Mismatch on Local JSON formatting differences

Issue: Express body-parser parses raw request buffers into objects, and serializing it back to string changes spacing, failing the signature hash check.

Fix Solution:Preserve the unmodified buffer at hook level via express.raw() configuration directly on webhook routes.

Recommended Related Projects

Continue building your skills with similar projects.

IntermediateFrontendStep-by-step

Admin Dashboard UI

Analytics dashboard with KPI cards, Recharts visualizations, data tables, and dark theme.

ReactRechartsTailwind CSS

Weekend Est. 10h4 steps

View Project

IntermediateBackendStep-by-step

High-Performance URL Shortener REST API

Node.js & Express REST API with MongoDB, nanoid key generation, and rate limiting.

Node.jsExpressMongoDBMongooseRedis+1 more

1 Day Est. 10h4 steps

View Project

AdvancedBackendStep-by-step

Distributed Async Job Queue

Background job pipeline with BullMQ, Redis, worker pools, retries, and dead-letter queues.

Node.jsBullMQRedisDocker

Weekend Est. 10h4 steps

View Project

Home/ Projects/ Backend/E-Commerce Payment Gateway Webhook Handler

Step-by-step guideIntermediateBackend Estimated: Weekend Est. 6h total

Progress:

E-Commerce Payment Gateway Webhook Handler

Secures payment gateway integrations using HMAC signature verification.

Tech Stack:Node.jsExpressCryptoMongoDB

Roadmap Steps

Key Features

Concepts

Tech Stacks

Common Pitfalls

Prequisites

Interactive Project Checklist

Tick off requirements as you build to track real-time completion.

Completed

Step-by-Step Development Roadmap

Follow this chronological guide to build the project from scratch.

0 / 4 Steps Completed

Step 1

Raw Body Middleware Parser

3 key tasks

Capture unmodified payload body buffers from payment gates.

Key Implementation Tasks

Configure Express to store raw request body as Buffer on req.rawBody
Ensure JSON parser does not touch specific /webhook URL paths to prevent validation mismatch
Log incoming headers and verify webhook format structure

Step 2

HMAC Signature Verification

3 key tasks

Step 3

Idempotency & Database Ledger Updates

3 key tasks

Step 4

Event Broadcasting & Queueing

3 key tasks

Common Challenges & Debugging Solutions

Real issues students hit during development and how to troubleshoot them fast.

State Management

Replay Attack Vulnerabilities

Issue: Hackers intercept valid webhook payloads and re-send them to trigger duplicate purchases or credits.

Fix Solution:Extract timestamp header from signature, verify it is within a 5-minute threshold, and validate hash includes the timestamp.

Database Connection

Out of Order Delivery Race Conditions

Issue: Webhook payment.succeeded fires before user signup API completes, referencing missing customer ID records.

Fix Solution:Implement upsert logic or temporary holding collections when reference IDs do not exist, retrying association periodically.

API Errors

Signature Mismatch on Local JSON formatting differences

Issue: Express body-parser parses raw request buffers into objects, and serializing it back to string changes spacing, failing the signature hash check.

Fix Solution:Preserve the unmodified buffer at hook level via express.raw() configuration directly on webhook routes.

Recommended Related Projects

Continue building your skills with similar projects.

IntermediateFrontendStep-by-step

Admin Dashboard UI

Analytics dashboard with KPI cards, Recharts visualizations, data tables, and dark theme.

ReactRechartsTailwind CSS

Weekend Est. 10h4 steps

View Project

IntermediateBackendStep-by-step

High-Performance URL Shortener REST API

Node.js & Express REST API with MongoDB, nanoid key generation, and rate limiting.

Node.jsExpressMongoDBMongooseRedis+1 more

1 Day Est. 10h4 steps

View Project

AdvancedBackendStep-by-step

Distributed Async Job Queue

Background job pipeline with BullMQ, Redis, worker pools, retries, and dead-letter queues.

Node.jsBullMQRedisDocker

Weekend Est. 10h4 steps

View Project