Fastify

better-payment/fastify returns a Fastify plugin that serves every payment route under the prefix you register it with.

1. Create the payment instanceCopy Anchor Link

// payment.ts
import { betterPayment, iyzico } from 'better-payment';

export const payment = betterPayment({
  mode: process.env.NODE_ENV === 'production' ? 'production' : 'sandbox',
  providers: {
    iyzico: iyzico({
      apiKey: process.env.IYZICO_API_KEY!,
      secretKey: process.env.IYZICO_SECRET_KEY!,
    }),
  },
  handler: {
    onCallback: async (result) => markOrder(result.paymentId, result.status),
    callbackRedirect: (result) => `/orders/${result.paymentId}?payment=${result.status}`,
  },
});

See configuration for every option and handler for allowedActions, transformRequest and the other handler hooks.

2. Register the pluginCopy Anchor Link

// server.ts
import Fastify from 'fastify';
import { toFastifyPlugin } from 'better-payment/fastify';
import { payment } from './payment';

const app = Fastify();
await app.register(toFastifyPlugin(payment), { prefix: '/api/pay' });

await app.listen({ port: 3000 });

Use the handler's basePath (default /api/pay) as the prefix.

Fastify rejects application/x-www-form-urlencoded bodies by default (415), but iyzico, Param, Akbank and PayTR post their callbacks in that format. The plugin accepts it for its own routes only, so your other routes keep Fastify's defaults.

3. Start a paymentCopy Anchor Link

The routes are served under /api/pay, so the frontend calls them directly:

const res = await fetch('/api/pay/iyzico/payment/init-3ds', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify(paymentRequest),
});

The typed client (better-payment/client) wraps the same routes.

4. Callback URLsCopy Anchor Link

Set callbackUrl to https://yoursite.com/api/pay/<provider>/payment/complete-3ds. The handler verifies the callback, calls onCallback and redirects the customer with callbackRedirect.

For PayTR, set the notification URL in the PayTR panel to https://yoursite.com/api/pay/paytr/callback.

Request body sizeCopy Anchor Link

Fastify applies its own bodyLimit (1 MiB by default). Bank callbacks are a few kB.