Building payments into your application requires more than calling a payment API. Your backend must correctly handle transaction states, verify webhook events, and account for failed, delayed, or repeated notifications.

I help startups and established businesses integrate payment providers into Node.js and NestJS applications.

Payment provider configuration and API integration

Payment initialization and transaction verification

Secure webhook signature verification

Idempotent webhook processing to reduce duplicate processing

Transaction status management and error handling

Sandbox testing and integration documentation

Guidance for production configuration and deployment

Integrated payment backend for the agreed workflows

Webhook handlers and transaction verification

Relevant database changes

Tests for agreed payment scenarios

Setup and handover documentation

One-time payments

Checkout and payment confirmation

Subscription payment integration, where supported and separately scoped

Transaction status synchronization

Payment notifications and backend event processing

$750 for one provider and a clearly defined payment workflow. Multiple providers, complex subscription systems, refunds, reconciliation, and legacy migrations may require a custom quote.

Tell me which payment provider you use, your backend framework, the payment flow you need, and whether the application is already in production.